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close this bookPublic Health Action in Emergencies Caused by Epidemics (WHO - OMS, 1986, 285 p.)
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View the documentAcknowledgements
View the document1. Introduction
Open this folder and view contents2. Explanation of terms and general lines of action
Open this folder and view contents3. Organization of an emergency health service
Open this folder and view contents4. Procedures for epidemiological investigations
Open this folder and view contents5. Analysis of investigation data
Open this folder and view contents6. General measures for the control of outbreaks
Open this folder and view contents7. Follow-up of control measures
View the documentANNEX 1 - Explanation of epidemiological terms1
View the documentANNEX 2 - Procedures for assembling epidemiological data and formulating and testing hypotheses of causation
View the documentANNEX 3 - Diseases that may cause epidemics1
View the documentANNEX 4 - Standard precautions, isolation and medical evacuation for diseases with person-to-person transmission
View the documentANNEX 5 - Collection and shipment of laboratory specimens
View the documentANNEX 6 - Identification of arthropod and rodent vectors of communicable diseases and use of insecticides and rodenticides
View the documentANNEX 7 - Decontamination procedures
View the documentANNEX 8 - Informal Consultation on Strategies for the Control of Emergencies Caused by Epidemics of Communicable Disease, 9-13 November 1981
View the documentWhere to Purchase WHO Publications
View the documentBack Cover

ANNEX 3 - Diseases that may cause epidemics1

1 Where possible, the appropriate ICD code is given, taken from: International Classification of Diseases, 9th rev., Geneva, World Health Organization, 1977.

Acquired immunodeficiency syndrome (AIDS)

Generalized lymphadenopathy of at least 3 months’ duration involving two or more extrainguinal sites, afebrile or with prolonged intermittent fever, ending with severe opportunistic infections (Pneumocystis carinii pneumonia , disseminated Mycobacterium avium intracellular infection, Kaposi’s sarcoma). Associated with a retrovirus. Laboratory: reactive hyperplasia of lymph nodes, abnormal T-lymphocyte helper/suppressor ratio. Incubation: possibly long. Transmission: sexual, blood and blood products, factors VIII and IX. Occurrence: first described in the United States of America in 1981, later identified in equatorial Africa and the Caribbean; in developed countries, clusters in homosexual males and intravenous drug addicts; cases have been described in female sexual partners of males with AIDS, children of infected mothers, and persons with haemophilia; in equatorial Africa, AIDS is acquired mainly through heterosexual contact. Control: investigation of contacts; same precautions for hospital and laboratory personnel as for viral hepatitis B. Reference: WHO Technical Report Series, No. 736, 1986 (Sixth report of the WHO Expert Committee on Venereal Diseases and Treponematoses).

Acute bacterial conjunctivitis (ICD 372.0)

Hyperaemia of the palpebral and bulbar conjunctivae of one or both eyes, photophobia, mucopurulent discharge. Caused by different bacteria: Haemophilus influenzae biotype III (Koch-Weeks bacillus), pneumococci, H. influenzae biotype I, Moraxella lacunata, staphylococci, streptococci, Pseudomonas aeruginosa and Corynebacterium diphtheriae. Differential diagnosis: gonococcal ophthalmia in the first 3 weeks of life. Laboratory: microscopic examination of a smear of discharge and isolation on appropriate culture media. Incubation: 1-3 days. Transmission: direct contact with discharges through contaminated fingers, possibly by droplets from the throat, indirect through soiled toilet articles, optical instruments, and flies. Occurrence: frequently epidemic, particularly in warm climates or communities with poor sanitation. Control: local application of sulfonamides or antibiotics; personal hygiene; vector control (flies, eye gnats). Safe disposal of ocular secretions during acute phase.

Acute schistosomiasis (ICD 120)

General malaise, spiking fever at night, profuse sweating, abdominal pain, myalgia, arthralgia, diarrhoea, dry cough, loss of weight, hepatomegaly, splenomegaly, urticaria, swollen eyelids; syndrome may last for 3-4 months. Complication: chronic stage (see Schistosomiasis, urinary and intestinal). Caused by: maturation, migration and early oviposition of Schistosoma haematobium, S. mansoni, and S. japonicum. Differential diagnosis: malaria, typhoid fever, salmonellosis, bacillary dysentery. Laboratory: high erythrocyte sedimentation rate, eosinophilia, microscopic detection of eggs in the stool or urine sediment, serological tests. Incubation period: 4-6 weeks after cercarial penetration in the skin (see Swimmers’ itch). Transmission: contact with infested water by bathing or drinking. Occurrence: possible clustering of cases among tourists visiting endemic schistosomiasis zones. Control: treatment with antischistosomal drugs (praziquantel) should be delayed to avoid massive liberation of antigens. Reference: STUIVER, P. C. Acute schistosomiasis (Katayama fever). British medical journal. 288: 221-222 (1984).

Acute viral gastroenteropathy (ICD 008.8)

Sudden onset, low-grade fever, nausea, vomiting, diarrhoea, abdominal cramps, headache, myalgia. Endemic forms are caused by rotaviruses (see Rotaviral enteritis), astroviruses, coronaviruses, adenoviruses, caliciviruses, and other small round viruses. Epidemics have been caused by Norwalk virus and related agents. Evidence is inconclusive for enteroviruses. Laboratory: immune electron microscopy and enzyme-linked immunosorbent assay (ELISA) for rotaviruses. Incubation: 48 hours or less. Transmission: direct by faecal-oral route or indirect via food and water. Occurrence: worldwide, greater in areas where hygiene is poor; predominantly in the United States of America for Norwalk virus (food-borne or water-borne outbreaks, sometimes with sharp onset; contagion has also occurred in swimming-pools). Control: no specific treatment; rehydration in severe cases; investigation of contacts and source of infection. Excreta precautions, enteric isolation for children during acute phase. Reference: WHO SCIENTIFIC WORKING GROUP. Rotavirus and other viral diarrhoeas. Bulletin of the World Health Organization, 58: 183-198 (1980).

Acute viral pharyngitis (ICD 462)

Sore throat, mild fever, local pain, difficulty in talking and swallowing, cervical lymphadenopathy (may be the initial stage of a systemic infection or bronchitis). Caused by viruses such as influenza viruses, parainfluenza viruses, respiratory syncytial virus, adenoviruses, cytomegalovirus, human (gamma) herpesvirus 4 (“Epstein-Barr virus”), other herpesviruses, measles virus, mumps virus, arboviruses, Lassa fever virus, Ebola virus, or bacteria or agents such as Mycoplasma pneumoniae. Incubation: a few days. Transmission: droplets, occasionally aerosols, articles freshly soiled with pharyngeal discharges; asymptomatic carriers are frequent. Occurrence: worldwide. Control: no specific treatment. Secretion precautions.

Acute viral rhinitis (ICD 460)

Rhinitis with nasal watery discharge, mild fever. Caused by rhino-viruses, coronaviruses, respiratory syncytial virus, parainfluenza viruses, adenoviruses and certain enteroviruses. Complications: sinusitis, otitis, tracheitis, bronchitis. Incubation: 12-72 hours. Occurrence: worldwide, explosive outbreaks. Treatment: symptomatic. Secretion precautions.

Adenoviral conjunctivitis (ICD 077.3)

Sudden onset, unilateral or bilateral inflammation of conjunctivae, oedema of the lids, pain, photophobia, occasionally low-grade fever, headache, malaise, duration about 2 weeks. Complication: petechial haemorrhages of the cornea. Caused by type 8 adenovirus and occasionally other serotypes. Laboratory diagnosis: isolation of virus from eye swabs or conjunctival scrapings inoculated in cell culture; serological tests. Incubation: 5-12 days. Transmission: direct or indirect contact with eye secretions. Occurrence: worldwide, sporadic cases or explosive outbreaks which can originate in eye clinics; household spread; dust has been incriminated. Control: no specific treatment, rigorous asepsis in eye clinics (hand-washing), personal toilet articles, disinfection of conjunctival and nasal discharges and articles soiled therewith. Precautions: ocular secretions.

Adenoviral respiratory disease

See Pneumonitis, viral

Amoebiasis (ICD 006.9)

Acute form with fever, chills, tenesmus, blood and mucus in stools, or mild and recurrent afebrile forms. Complications: liver abscess, intestinal perforation. Fatalities linked to complications. Caused by Entamoeba histolytica, a protozoon. Differential diagnosis: shigellosis, balantidiasis, giardiasis, strongyloidiasis. Laboratory: microscopic demonstration of trophozoites and cysts in fresh faecal specimens on repeated examinations. Incubation: 2-4 weeks or longer. Transmission: faecal-oral, contaminated water, drinks (milk) and raw vegetables (cysts), food handlers, flies, asymptomatic carriers. Occurrence: all ages, prevalent in warm climates and under poor sanitary conditions, clusters of cases. Control: specific treatment, excretion precautions, investigation of source and contacts, protection and disinfection of water (boiling is preferred, since chlorination may be insufficient), cooking of vegetables, fly control. Precautions: excreta. Reference: WHO SCIENTIFIC WORKING GROUP. Parasite-related diarrhoeas. Bulletin of the World Health Organization, 58: 819-830 (1980).

Angiostrongyliasis (ICD 128.8)

Onset with low-grade fever, severe headache, stiffness of the back and neck, various paraesthesias, temporary facial paralysis. Not lethal; infection may be asymptomatic. Caused by a nematode (lung worm) of rats, Angiostrongylus cantonensis. Differential diagnosis: tuberculous meningitis, coccidioidal meningitis, aseptic meningitis, cerebral cysticercosis, hydatidosis, gnathostomiasis. Laboratory: eosinophils, and possibly the worm, in the cerebrospinal fluid. Transmission: ingestion of insufficiently cooked snails, prawns, fish, vegetables. No direct transmission. Occurrence: endemic in Australia, Egypt, East Asia, Pacific islands and Madagascar. Control: boiling of incriminated food.

Anthrax, cutaneous (ICD 022.0)

Itching of the exposed skin surface, appearance of a papular lesion, which becomes vesicular and gives a depressed black eschar in 2-6 days, surrounded by moderate oedema and sometimes secondary vesicles. Complications: if untreated, septicaemia; see also Anthrax, intestinal and pulmonary. Caused by Bacillus anthracis. Differential diagnosis: orf (contagious pustular dermatitis). Laboratory: demonstration of bacillus in local lesion or discharges by microscopic examination after Gram staining; blood culture. Incubation period: 2-5 days. Transmission: common-source infection, contact of skin with infected animal tissues or products made from them, or contaminated soil. Occurrence: worldwide, sporadic or clusters of cases as occupational hazard in farmers, veterinarians, workers in agriculture-related industries (manufacture of animal feeding stuffs), campers. Control: treatment with penicillin or tetracyclines, isolation of discharges; disinfection of discharges and soiled articles by autoclaving to destroy spores, terminal cleaning; immunization of those at occupational risk; prompt immunization of all animals at risk; carcasses should be burned or buried deeply with anhydrous calcium oxide. Precautions: skin discharges.

Anthrax, intestinal (ICD 022.2)

Fever, signs of septicaemia, abdominal symptoms, gastroenteritis with vomiting and blood in the stools. Mortality is high. Transmission: ingestion of contaminated undercooked meat. Occurrence: rare, discrete foci, especially in developing countries.

Anthrax, pulmonary (ICD 022.1)

Onset: mild fever and non-specific symptoms, resembling common upper respiratory tract infection, followed in 3-5 days by acute respiratory distress, shock and death. Caused by Bacillus anthracis. Laboratory: microscopic examination of sputum, isolation of agent by culture or animal inoculation (maximum containment laboratory). Incubation: 2-7 days, usually 2-5. Transmission: inhalation of spores. Occurrence: in foci of zoonotic anthrax, all climates, occupational hazard in agricultural workers, laboratory infections; may cause major outbreaks and nosocomial infections. Control: tetracyclines, STRICT ISOLATION, investigation of contacts and source of infection, terminal disinfection.

Argentine and Bolivian haemorrhagic fevers

See Junin and Machupo haemorrhagic fevers.

Arthropod-borne viral encephalitides (ICD 062/063)

Sudden onset, high fever, headache, meningeal signs, tremors, convulsions in infants, spastic paralysis (occasionally flaccid, as in Far Eastern tick-borne encephalitis), stupor, disorientation, coma. Other cases begin with an initial influenza - or dengue-like stage, followed by nervous system symptoms 4-10 days after apparent recovery. Mild cases do not proceed beyond the stage of aseptic meningitis. Severe infections may leave sequelae. Fatality rate: 0.5-60%. Caused by viruses belonging to different genera: Japanese encephalitis virus in the western Pacific, south-east Asia and India; Murray Valley encephalitis virus in Australia and Papua New Guinea; western equine encephalomyelitis virus in the USA and Canada; eastern equine encephalomyelitis virus, St Louis virus and California encephalitis viruses in the Americas; Rocio virus in Brazil; tick-borne encephalitis virus complex and Far Eastern tick-borne encephalitis in Europe, West Nile virus in Africa, south-west Asia, Europe and India. Differential diagnosis: non-paralytic poliomyelitis, rabies, mumps meningoencephalitis, lymphocytic choriomeningitis, aseptic meningitis due to enteroviruses, herpesviral encephalitis, postvaccinal or postinfection encephalitides, bacterial, protozoal, leptospiral, and mycotic meningitides. Laboratory: mild leukocytosis (50-100/mm3) in cerebrospinal fluid; sometimes isolation of virus from brain tissue of fatal cases, rarely from blood; serological tests. Incubation: 5-15 days. Transmission by bites of mosquitos and ticks infected on animals (e.g., birds, rodents); no person-to-person transmission. Central European tick-borne encephalitis may also be transmitted by milk from infected goats or sheep. Occurrence: worldwide but greater in warm climates or in summer and limited to certain specific foci; sporadic or epidemic in all age groups but certain viruses predominantly affect children. Control: no specific treatment; protection against vectors; vaccination for Japanese encephalitis and restricted to laboratory workers for some of the other diseases. No isolation. References: MONATH, T. P. Arthropod-borne encephalitides in the Americas. Bulletin of the World Health Organization, 57: 513-533 (1979); WHO Technical Report Series, No. 719, 1985 (Arthropod-borne and rodent-borne viral diseases: report of a WHO Scientific Group).

Arthropod-borne viral fever (ICD 066)

Signs and symptoms are similar to those of dengue (dengue-like fevers): sudden onset, fever, headache, muscular and joint pains, vomiting, and occasionally rash and lymphadenopathy. Usually not lethal. Caused by about 80 viruses belonging to several genera. Differential diagnosis: most frequently, influenza and malaria. Laboratory: isolation of virus from blood during the first 3-5 days; serological tests (IgM in single serum or IgG elevation in paired sera). Incubation: 2-15 days, usually 3-6. Transmission: by different arthropods: mosquitos, ticks, Phlebotomus (sandflies) and Culicoides (gnats). No direct person-to-person transmission. Occurrence: in all types of climate, depending on viruses prevalent locally, their vertebrate reservoirs and arthropod vectors; explosive outbreaks possible. Control: no specific drug, identification of vector and appropriate vector-control measures. See also dengue fever. Isolation under bed-net during the first few days when domestic mosquitos may be vectors. Reference: WHO Technical Report Series, No. 719, 1985 (Arthropod-borne and rodent-borne viral diseases: report of a WHO Scientific Group).

Aseptic viral meningitis

See Meningitis, viral.

Balantidiasis (ICD 007.0)

Diarrhoea, abdominal pains, vomiting, tenesmus, mucus and blood in stools. Fatality rate low. Caused by Balantidium coli, a protozoon. Incubation: unknown, perhaps a few days. Transmission: ingestion of cysts from contaminated swine, contaminated water, meat, vegetables, flies, soiled hands of food handlers. Occurrence: worldwide, rare except under poor sanitary conditions, water-borne epidemics possible. Control: metronidazole and tetracyclines, excreta precautions, protection against water and food contamination, fly control.

Bartonellosis (ICD 088.0)

There are two forms: Oroya fever, with severe anaemia and generalized lymphadenopathy, and verruga peruana, with muscular and joint pains, disseminated haemangioma-like dermal or deep-seated nodular lesions. Fatality rate of untreated Oroya fever: 10-40%; verruga is rarely fatal. Caused by Bartonella bacilliformis within red blood cells. Incubation period: 16-22 days, up to 4 months. Transmitted by bite of sandfly (Phlebotomus); man is the reservoir. Occurs only at high altitudes in mountain valleys in south-west Colombia, Ecuador, and Peru. Control: treatment with antibiotics, house spraying with insecticides.

Bornholm disease

See Epidemic myalgia.


See Food poisoning.

Boutonneuse fever

See Spotted fever group.

Bronchiolitis (ICD 466.1)

A respiratory disease of infancy; fever, cough, rapid breathing, expiratory wheezing, cyanosis, X-ray shows atelectasis and emphysema. High fatality rate-an infant may die overnight. Caused by respiratory syncytial virus, occasionally by parainfluenza viruses (mainly type 3) and influenza virus. Occurrence: worldwide; epidemics in spring, autumn and winter; nosocomial infections. Laboratory: virus isolation or specific immunofluorescence in nasopharyngeal aspirates. Control: secretion precautions, or respiratory isolation.

Bronchitis (ICD 466.0)

Generally follows an infection of the nasopharynx, slight fever, cough initially dry and becoming mucopurulent. Complication: chronic bronchitis in adults. Caused by viruses (influenza and parainfluenza viruses, respiratory syncytial viruses, adenoviruses, measles virus), Mycoplasma pneumoniae, or bacteria (Haemophilus influenzae and pneumococci). Laboratory: isolation of agent by cultivation of sputum in bacterial or viral media; serological tests. Incubation: a few days. Transmission: droplets, articles freshly soiled by discharges. Occurrence: worldwide, seasonal, clusters of cases in closed communities. Control: secretion precautions, antibiotics if bacterial pulmonary complications develop.

Brucellosis (ICD 023.9)

Acute or insidious onset, undulant fever, profuse sweating and weakness. Complications: meningitis, pneumonitis and local infections. Fatality rate without treatment, 2% or less. Caused by different serotypes of a bacterium, Brucella abortus. Differential diagnosis: long-term “sweating” fevers, e.g., malaria. Laboratory: isolation of agent from blood or discharges; serological tests on paired sera in laboratories with appropriate expertise and facilities. Incubation: 5-30 days. Transmission: milk or milk products; occupational disease (contact with infected domestic animals), possibly airborne, no person-to-person transmission, laboratory infections. Occurrence: worldwide. Control: search for source of infection (animal or dairy products), tetracyclines. Isolation: not required. Reference: WHO Technical Report Series (Sixth report of the Joint FAO/WHO Expert Committee on Brucellosis) (in press).

Campylobacter enteritis (ICD 027.8)

Fever or normal temperature, malaise, headache, backache, abdominal pains, vomiting, and after 1-3 days profuse diarrhoea, with liquid foul-smelling stools and blood streaks, which may last from a few days to 3 weeks. Complications: typhoid-like syndrome, septicaemia, endocarditis. Fatality rate does not seem high. Caused by a curved-rod vibrio-like bacillus, Campylobacter jejuni. Laboratory: isolation of the organisms by culture on special media. Incubation: 2-11 days. Transmission: direct contact, faecal-oral route (children to parents), contact with infected chickens, undercooked food, milk, water; frequent inapparent infections. Occurrence: probably worldwide, all ages, but especially children, sporadic cases, common-source outbreaks in families and institutions. Control: erythromycin, excretion precautions, search for source of infection and contacts. Reference: WHO SCIENTIFIC WORKING GROUP. Enteric infections due to Campylobacter, Yersinia, Salmonella and Shigella. Bulletin of the World Health Organization, 58: 519-537 (1980).

Capillariasis (ICD 128.8)

There are three forms: enteropathy causing malabsorption, ascites, pleural transudate; acute or subacute hepatitis with eosinophilia; and pulmonary form with fever and asthmatic symptoms. Heavy infections may be fatal. Caused by Capillaria nematodes. Laboratory: detection of eggs in the sputum or faeces. Incubation period: 3-4 weeks. Contamination by ingesting soil-contaminated food or water; rats, dogs, cats and carnivores are reservoirs. Occurrence: hepatic and pulmonary forms are very rare, but worldwide; intestinal form is epidemic in the Philippines. Control: protect water supplies and food from animal faeces and dirt. Isolation not necessary.

Cercarial dermatitis

See Swimmers’ itch.

Cercopithecid herpesvirus 1 disease (ICD 054.3;1 323.42)

1 Primary code for underlying disease.
2 Secondary code referring to the manifestation in the affected organ.

Acute febrile onset followed by neurological symptoms and ascending encephalomyelitis, almost invariably rapidly fatal or leaving sequelae. Caused by Herpesvirus simiae. Laboratory: isolation of virus. Incubation period: up to 3 weeks. Transmission by bite of Old World monkeys, exposure of naked skin to saliva or monkey tissues. Occurrence: occupational disease, veterinarians, laboratory workers. Control: quarantine and precautions in handling monkeys.

Chagas’ disease

See Trypanosomiasis, American.


See Varicella.

Chikungunya haemorrhagic fever (ICD 065.4)

Infection with Chikungunya virus (an arbovirus belonging to the genus Alphavirus) is common in Africa and Asia, with dengue-like symptoms. Haemorrhagic signs, petechiae, haematemesis and melaena have occurred only during epidemics in India and east Asia; there is no shock, and fatality rate is very low. Transmission: Aedes mosquitos. Laboratory: isolation of virus from blood, demonstration of antibodies. Control: symptomatic treatment; isolation under bed-nets during the first few days, protection from Aedes mosquitos. References: Dengue haemorrhagic fever: diagnosis, treatment and control. Geneva, World Health Organization, 1986; WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Chlamydial conjunctivitis (ICD 077.0)

In adults: follicular conjunctivitis with minimal discharge, preauricular lymphadenopathy, symptoms sometimes persist for a year or longer. In the newborn: abundant mucopurulent discharge, possible superficial corneal involvement, may be followed by chlamydial pneumonia up to the age of 12 months. Caused by Chlamydia trachomatis immunotypes B-K. Differential diagnosis: trachoma caused by Chlamydia trachomatis immunotypes A, B and C and characterized by conjunctival follicular inflammation leading to deformity of the eyelids, corneal invasion and blindness, highly endemic in warm climates (trachoma). Laboratory diagnosis: demonstration of intracytoplasmic inclusion bodies in the epithelial cells of conjunctival or genital scrapings by Giemsa staining or immunofluorescence and isolation of the agent. Incubation: 5-12 days. Transmission: in adults, eyes are infected by fingers contaminated with genital secretion (chronic carriers may be asymptomatic); in the newborn, direct contact with the infected birth canal. Occurrence: worldwide; outbreaks in non-chlorinated swimming-pools. Control: adults and children, sulfonamides or antibiotics orally and antibiotic ointments; secretion precautions.

Cholera (ICD 001.0)

Sudden onset, profuse watery stools, occasional vomiting, rapid dehydration, acidosis, circulatory collapse; no fever, except sometimes in children. Untreated, fatality rate may exceed 50% and death may occur within a few hours; treated, the rate is below 1% Mild cases with only diarrhoea and asymptomatic infections are frequent. Caused by Vibrio cholerae O-group 1 (biotypes eltor or classical). Differential diagnosis: non-O-group 1 V. cholerae strains, which can cause limited outbreaks of cholera-like disease, sometimes with fever and mucus and blood in stools, but no large epidemics. Laboratory: dark-field or phase-microscopy examination of faeces or vomitus shows characteristic vibrio motility inhibited by specific antiserum; culture on special media; serological tests showing a rise of antibody in paired sera. Incubation: a few hours to 5 days. Transmission: faecal-oral, water, food, flies. Occurrence: endemoepidemic in Africa, Asia, Eastern Europe and India; imported in the Americas and Western Europe; rare outbreaks associated with air travel. Control: rehydration fluid (oral, intravenous), tetracyclines, trimethoprim-sulfamethoxazole, no isolation (except in non-endemic areas), excretion precautions, disinfection of hands, boiling or chlorination of water, search for source of infection and contacts for chemoprophylaxis; immunization is inappropriate; notification to WHO (disease subject to the International Health Regulations). References: A manual for the treatment of acute diarrhoea, unpublished WHO document, WHO/CDD/SER/80.2; Guidelines for cholera control, unpublished WHO document, WHO/CDD/SER/80.4; WHO SCIENTIFIC WORKING GROUP. Cholera and other vibrio-associated diarrhoeas. Bulletin of the World Health Organization, 58: 353-374 (1980).

Clonorchiasis (ICD 121.1)

Heavy infections may initially cause fever, chills, hepatomegaly, diarrhoea, mild jaundice and eosinophilia, followed by chronic inflammation of the biliary tree. Caused by Clonorchis sinensis, a trematode worm. Laboratory: demonstration of eggs in faeces or duodenal drainage fluid. Incubation period: about 1 month. Transmission: eating undercooked freshwater fish in endemic zone. Occurrence: South-East Asia; dried or pickled fish may cause imported cases. Control: locate source of infected fish, thorough cooking. Isolation not necessary.

Coccidioidomycosis (ICD 114)

Onset may be asymptomatic or resemble influenza followed by erythema nodosum. Complications: disseminated subcutaneous and visceral lesions, meningitis. Caused by: Coccidioides immitis, a fungus. Laboratory: direct examination or culture of sputum, pus, urine or cerebrospinal fluid; skin test with coccidioidin, serological tests. Incubation period: 1-4 weeks. Transmission: inhalation of spores from soil. No person-to-person transmission. Occurrence: arid and semi-arid areas of north, central and tropical South America; outbreaks may occur in endemic areas in large groups of susceptible persons from non-endemic areas. Control: treatment with fungicidal drugs.

Common cold

See Acute viral rhinitis.


See Acute bacterial conjunctivitis, Adenoviral conjunctivitis, Chlamydial conjunctivitis.

Crimean-Congo haemorrhagic fever (ICD 065.0)

Sudden onset, influenza-like initial phase with occasional vomiting and diarrhoea. Acute phase: petechial rash, large purpura areas, bleeding from gums, nose, lungs and uterus, haematemesis, haematuria, melaena, shock. Fatality rate: 2-50%; severe form in Central Asia, mild form in Central Africa. Caused by Congo virus (family Bunyaviridae). Laboratory: safety precautions, isolation of virus from blood and necropsy material and serological tests (containment laboratory). Incubation: 7-12 days. Transmission: by ticks infected by feeding on birds, rodents and domestic animals; person-to-person by contact with blood (hospital and laboratory infections). Occurrence: all ages; limited natural foci in rural areas. Treatment: supportive care; convalescent serum. Control: STRICT ISOLATION; protection against ticks (repellents, special clothing); disinfection of bloody discharges. References: AL TIKRITI, S. K. ET AL. Congo-Crimean haemorrhagic fever in Iraq. Bulletin of the World Health Organization, 59: 85-90 (1981); WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).


See Laryngotracheobronchitis.

Cryptococcosis (ICD 117.5)

Usually a subacute or chronic meningoencephalitis preceded by pulmonary infection sometimes by several months. Caused by a fungus: Cryptococcus neoformans. Laboratory: microscopic examination of cerebrospinal fluid mixed with Indian ink. Incubation: unknown. Transmission: inhalation of saprophytic fungus in the external environment (soil and pigeon droppings); infection also occurs in domestic animals; no person-to-person transmission. Occurrence: worldwide, usually sporadic, adults. Control: treatment with fungicidal drugs.

Delta agent hepatitis

See Viral hepatitis B.

Dengue fever (ICD 061)

Sudden onset, chills, fever, intense headache, joint and muscle pains, prostration and early erythema in certain cases. On 3rd or 4th day, transient defervescence (saddle-back fever). A macular eruption is frequent, sometimes petechiae appear on feet and legs, lymphadenopathy is also frequent. Fatality rate is usually zero. Complication: dengue haemorrhagic fever. Caused by the four serotypes of dengue virus (an arbovirus, genus Flavivirus). Differential diagnosis: other arthropod-borne viral fevers, influenza, typhus, sandfly (phlebotomus) fever and rubella. Laboratory: isolation of virus from blood during the first 3-5 days in laboratories with appropriate expertise; serological tests (IgM in single serum or IgG elevation in paired sera). Incubation: 3-15 days (mean 5-6). Transmission: indirect, from person to person mainly by Aedes aegypti, or by other Aedes mosquitos according to region. Occurrence: endemic areas in tropical regions (Africa, middle America, Asia); all age groups (frequently mild in children), sharp outbreaks when spreading to new areas or in newly exposed groups, spreading by transport of infected mosquitos or viraemic patients. Control: no specific treatment, symptomatic treatment (aspirin may cause bleeding and is contra-indicated); isolation under bed-nets during 3-5 days; individual protection against mosquitos; Aedes control measures in community; notification is optional. Reference: information on outbreaks is published by WHO in the Weekly epidemiological record.

Dengue haemorrhagic fever (ICD 065.4)

The haemorrhagic syndrome affects mainly non-Caucasian children 6 months to 12 years old in highly endemic dengue areas, and less frequently adults. In the initial phase, the child may have fever, upper respiratory symptoms, headache, vomiting and abdominal pain. Myalgia and arthralgia, characteristic of classical dengue, are uncommon. This minor illness, during which the child is often not confined to bed, lasts 2-4 days and many children recover without any further symptoms. In some, however, the condition suddenly deteriorates on the 3rd or 4th day when the temperature falls and there is abdominal pain, restlessness, lowering of the pulse pressure, peripheral vascular congestion, cold and clammy extremities, elevated erythrocyte volume fraction resulting from plasma leakage through capillaries, leading to hypovolaemic shock which is reversible for a few hours, petechiae, positive tourniquet test, thrombocytopenia, protracted bleeding time, haematemesis, and melaena resulting from disseminated intravascular coagulopathy. Fatality rate: untreated, 10-20%; treated, as low as 1%. Caused by the four serotypes of dengue virus (genus Flavivirus). Laboratory: isolation of virus from blood in early phase; serological tests for IgM in single serum and elevation of IgG in paired sera. Incubation: 6 days (range 3-15). Transmission: indirect, from person to person by several species of Aedes mosquitos, mainly Aedes aegypti; no direct transmission. Occurrence: mainly tropical zones of South-East Asia, and recent extension to South Pacific islands and the Caribbean (Cuba); still unknown in tropical Africa, in spite of the presence of dengue virus types 1, 2 and 4. Control: treatment of hypovolaemic shock by urgent intravenous rehydration carefully monitored to avoid pulmonary oedema; isolation under bed-nets during first few days; individual protection against mosquitos; space-spraying of insecticides during epidemics and breeding-site reduction; a vaccine is under development. Reference: Dengue haemorrhagic fever: diagnosis, treatment and control. Geneva, World Health Organization, 1986.

Diarrhoea due to parasites (ICD 127.9)

In addition to amoebiasis, balantidiasis, fascioliasis, fasciolopsiasis, schistosomiasis, and giardiasis, described elsewhere in this Annex, diarrhoeas may be caused by other parasites, such as intestinal nematodes (roundworms). Abdominal pain and diarrhoea preceded by dermatitis if larvae penetrate through the skin and pulmonitis if they migrate through the lungs to reach the intestine. Occurrence: more frequent in warm climates in areas of poor sanitation, numerous asymptomatic carriers, endemic, highly endemic and epidemic in newcomers (tourists). Transmission may be from person to person except for worms that have a developmental stage in animals or in soil. Agents: Trichuris trichiura (whipworm), Ascaris lumbricoides, Ancylostoma duodenale (hookworm, causing severe iron-deficiency anaemia), Strongyloides stercoralis (threadworm). Control: specific treatment, faecal hygiene. Reference: WHO SCIENTIFIC WORKING GROUP. Parasite-related diarrhoeas. Bulletin of the World Health Organization, 58: 819-830 (1980).

Diphtheria (ICD 032.3)

Mild fever, patches of greyish membrane on inflammatory zones in pharynx, tonsillar areas, larynx, or nose; cervical lymphadenopathy, oedema of the neck, toxic status. Complication: obstruction of larynx (croup, crow cough). Fatality rate: 5-10%. Differential diagnosis: Vincent’s angina, candidiasis, Lassa fever. Caused by Corynebacterium diphtheriae. Laboratory: Gram staining has little presumptive value; inoculation of special media; whenever clinical suspicion is aroused, treatment should be initiated without waiting for laboratory results. Incubation: 2-5 days or longer. Transmission: droplets, articles freshly soiled with discharges. Occurrence: worldwide, less frequent in warm climates (cutaneous diphtheria is more frequent). Control: STRICT ISOLATION, diphtheria antitoxin, antibiotics, oxygen, tracheostomy if necessary, active immunization, chemoprophylaxis with erythromycin, surveillance of contacts for 7 days, and search for carriers by throat swabbing and laboratory examination.

Dracontiasis (ICD 125.7)

Fever, nausea, vomiting, diarrhoea, dyspnoea, generalized urticaria and eosinophilia, burning and itching in a lower extremity, usually the foot, and occurrence of a blister where the adult female worm (1 m in length) will appear. Caused by Dracunculus medinensis, a nematode worm. Incubation: about 12 months. Transmission: infected Crustacea of the genus Cyclops in drinking-water or step wells and ponds, no person-to-person transmission. Occurrence: localized foci in warm climates. Control: treatment; filtration or boiling of drinking-water, treatment of water with chlorine.

Ebola and Marburg virus diseases (ICD 078.8)

Sudden onset, fever, general pains, vomiting, watery diarrhoea, rapid dehydration, prostration. On 5th-7th day maculopapular rash (may look like measles with conjunctivitis), pharyngitis, ecchymoses, petechiae, bleeding from the nose and gums, haematemesis, melaena, metrorrhagia, circulatory failure, shock, death between days 7 and 16. Oedemas (facial swelling, pleuritic and pericarditic) are more commonly seen in Marburg disease. Fatality rate: 30% (Marburg disease) to 85% (Ebola disease). Caused by two morphologically similar but antigenically distinct viruses (family Filoviridae). Laboratory: isolation of virus from blood and necropsy specimens; serological tests (in maximum-containment laboratory). Incubation: 2-21 days, usually 3-7. Transmission: unknown animal source (monkeys incriminated for Marburg disease); person-to-person transmission through several generations of cases for Ebola disease, rarely exceeding the second generation for Marburg disease, by face-to-face contact (droplets, aerosols) or contact with blood. Occurrence: probably prevalent in most parts of sub-Saharan Africa, may be asymptomatic; isolated outbreaks may occur abruptly. Control: intensive supportive care, STRICT ISOLATION, investigation of contacts, immune plasma and antiviral drugs may be beneficial early in the disease. References. SIMPSON, D. I. H. Marburg and Ebola virus infections: a guide for their diagnosis, management and control. Geneva, World Health Organization, 1977 (WHO Offset Publication No. 36); Ebola haemorrhagic fever in Sudan, 1976: report of a WHO/International Study Team. Bulletin of the World Health Organization, 56: 247-270 (1978); Ebola haemorrhagic fever in Zaire, 1976: report of an International Commission. Bulletin of the World Health Organization, 56: 271-293 (1978). WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Echinococcosis (ICD 112.9)

A disease caused in man by cysts of the larval stage of tapeworms which parasitize dogs and other carnivores.

In unilocular echinococcosis, there are a limited number of well-encapsulated cysts, most frequently located in the liver and lungs. They may be well tolerated for a certain time or cause severe symptoms and death. The parasite is Echinococcus granulosus, a tapeworm of the dog. Laboratory diagnosis is by microscopic identification of hooklets in cysts, membranes or sputum after rupture, serological tests, intradermal tests and histopathological examination. The incubation period extends from months to years. Transmission to man occurs by ingestion of parasite eggs disseminated by infected dogs or other carnivores in their fur, in food and water. Carnivores are infected by eating viscera of sheep, cattle and pigs infected with cysts. Occurrence: worldwide. Control: no specific treatment, surgical removal of voluminous cysts when feasible, limitation of access of dogs to viscera of grazing animals.

In alveolar hydatid disease, there are a large number of poorly circumscribed microvesicles (cysts), mainly in the liver but also in other organs. The prognosis depends on the number and location of the cysts and is generally grave. The parasite is Echinococcus multilocularis, a tapeworm of foxes, dogs and cats. Laboratory diagnosis is as above. Long incubation period. Transmission to man by ingestion of infective eggs excreted by carnivores which are infected by eating parasitized voles or mice, or through contact with contaminated water, raw vegetables and wild fruits. Occurrence: worldwide. Control: no specific treatment in man, treatment of domestic dogs and cats, precautions in handling foxes.

Polycystic echinococcosis, in which there is rapid proliferation and growth of cysts, occurs in the Americas and is caused by Echinococcus vogeli, transmitted to man by hunting dogs.

Encephalitis, viral (ICD 049)

A general term which includes encephalitides caused by alpha-viruses, bunyaviruses and flaviviruses (see Arthropod-borne viral encephalitides) and other viruses such as human alphaherpesviruses 1-3, enteroviruses 70 and 71, mumps virus, and cercopithecid herpesvirus 1 (simian B disease). See also Meningoencephalitis due to miscellaneous infectious agents.

Enteritis due to Escherichia coli (ICD 008.0)

Three types of E. coli cause somewhat different syndromes. Enteroinvasive strains: fever, mucoid and occasionally bloody diarrhoea, as in shigellosis. Enterotoxigenic strains: profuse watery diarrhoea with or without fever, abdominal cramps, vomiting, acidosis, prostration, dehydration, similar to cholera. Enteropathogenic strains: associated with classical severe outbreaks of acute diarrhoea in newborns in nurseries and in summer. Laboratory: isolation of strains from stools and typing with specific sera; antibiotic sensitivity is important. Incubation: 12-72 hours. Transmission: faecal-oral, person-to-person or common-source by contaminated food-handlers (infection may be asymptomatic), water, food and flies. Occurrence: worldwide, outbreaks in nurseries and institutions, individual or clusters of cases of traveller’s diarrhoea. Control: oral or intravenous rehydration, antibiotics; scrupulous hygiene practices in nurseries (hand-washing), strict enteric precautions in hospitals, disinfection of discharges and soiled articles. Reference: WHO SCIENTIFIC WORKING GROUP. Escherichia coli diarrhoea. Bulletin of the World Health Organization, 58: 23-36 (1980).

Enteroviral exanthematous fever (ICD 048)

Febrile, rubelliform or morbilliform rash usually confined to the face, neck and chest, exceptionally haemorrhagic or vesicular. The course is generally benign but aseptic meningitis may occur. Caused by certain serotypes of coxsackievirus and echovirus. Laboratory: isolation of virus from blood, stools, throat and vesicles; serological tests on paired sera to show an increase in antibody. Incubation: 3-5 days. Transmission: direct person-to-person by faecal-oral route, or droplets; indirect through food, water, flies, swimming-pools, articles contaminated by discharges. Occurrence: worldwide, higher incidence in summer, all ages, clusters of cases in closed communities. Control: no specific treatment, personal and community hygiene; discharge precautions.

Enteroviral haemorrhagic conjunctivitis (ICD 077.4)

Sudden onset, hyperaemia of conjunctivae, seromucous discharge, subconjunctival haemorrhages, occasionally keratitis and uveitis, ocular signs and symptoms resolve in 1-2 weeks. Complications: lumbosacral radiculomyelitis (poliomyelitis-like) in some cases, mainly in South-East Asia. Caused by enterovirus 70; similar disease may be caused by coxsackievirus A24, adenovirus 11, 4 or 10. Laboratory: electron microscopy of conjunctivitis scrapings, inoculation of cell cultures (virus growth may be difficult); serological tests. Incubation: 1-2 days. Transmission: direct or indirect contact with eye discharges, optical instruments, possibly by droplets from the throat of infected persons. Occurrence: worldwide, all ages; explosive outbreaks in communities with poor hygiene, or clusters that can be traced to contaminated eye clinics. Control: no specific treatment, personal hygiene, appropriate disinfection of optical instruments, infected children should not attend school.

Enteroviral lymphonodular pharyngitis (ICD 074.8)

Pharyngitis characterized by raised, discrete, whitish or yellowish nodules surrounded by a narrow annular erythematic zone. Caused by coxsackievirus A10. Laboratory: cultivation of virus. Incubation period: 5 days. Transmission: droplet spread, nose and throat discharges, faeces of infected person; man is the only reservoir. Infectious period: acute stage, longer for stools. Occurrence: worldwide, outbreaks in children in summer and early autumn in nursery schools. Control: reduce person-to-person contact, disinfection of discharges, faeces and soiled articles.

Enteroviral paralytic encephalomyelitis (ICD 048;1 323.42)

1 Primary code for underlying disease.
2 Secondary code referring to the manifestation in the affected organ.

Enterovirus infections, especially with echoviruses and coxsackieviruses (mainly A7, A9, B2-5) and enterovirus 71, may cause flaccid paralysis mainly in children, which can be severe, but may disappear after 2-3 weeks without sequelae. Differential diagnosis: poliomyelitis, Far Eastern tick-borne encephalitis (caused by a flavivirus transmitted by ticks in Asian USSR and central Europe), in which there may be flaccid paralysis mainly of the shoulder girdle, with sequelae; botulism is afebrile and shows very early symmetrical cranial nerve flaccid paralysis; tick-bite paralysis occurs uncommonly but worldwide and is manifested by a flaccid ascending motor paralysis which disappears when the tick is removed. Control: excreta and secretion precautions until clinical recovery.

Enteroviral vesicular pharyngitis (ICD 074.0)

Sudden onset, fever, malaise, sore throat, greyish papulovesicular pharyngeal lesions on erythematous base and ulcers. Not fatal. Caused by coxsackieviruses, group A, and occasionally other enteroviruses. Incubation: 3-5 days. Transmission: droplets, articles freshly soiled with pharyngeal discharges, and faecal-oral. Occurrence: worldwide, mainly in children. Control: no specific drug, personal hygiene.

Enteroviral vesicular stomatitis with exanthem (ICD 074.3)

Sudden onset of fever, oral vesicular lesions and papules, vesicular lesions persisting for 7-10 days on palms and soles, occasionally on the buttocks. Caused by coxsackieviruses and other enteroviruses. Differential diagnosis: foot and mouth disease. Laboratory: isolation of the virus from lesions and faeces; serological tests on paired sera. Transmission: person-to-person by direct contact with nose and throat discharges, droplet spread, local lesions and faeces, no reliable evidence of common-source infection. Occurrence: worldwide, in summer and early autumn, outbreaks among groups of children. Incubation: 3-5 days. Control: no specific treatment, reduce person-to-person contact and crowding, standard isolation, disinfection of discharges.

Epidemic exanthema with meningitis

See Enteroviral exanthematous fever.

Epidemic keratoconjunctivitis

See Adenoviral conjunctivitis.

Epidemic myalgia (ICD 074.1)

Sudden onset, fever, headache, paroxysmal pain in the chest or in the abdomen, simulating appendicitis in children. No fatalities. Complications: myocarditis, aseptic meningitis. Caused by group B coxsackieviruses. Laboratory: isolation of the virus from faeces and throat washings, concomitant with increase in antibody in paired sera. Incubation: 3-5 days. Transmission: faecal-oral, respiratory droplets, articles freshly soiled, sewage, flies, asymptomatic carriers. Control: no specific drug (oral poliovirus vaccine may be used to try and stop the spread), personal hygiene, community sanitation, excreta precautions.

Erythema chronicum migrans due to Borrelia burgdorferi (ICD 695.9)

Progressive onset with fever, malaise and a red macule or papule expanding into a large annular lesion, sometimes multiple. Complications: polyarthritis, aseptic meningitis, encephalitis, cardiopathy. Caused by a spirochaete (Borrelia) and transmitted by Ixodes ticks. Differential diagnosis: none, the skin lesion is distinctive. Laboratory: no test available. Incubation; 3-21 days after tick bite. Transmission: tick-borne, no person-to-person transmission. Occurrence: endemic foci in the USA; a similar neurological disease but without rash (tick-borne meningopolyneuritis) exists in eastern Europe. Control: treatment with penicillin or tetracycline.

Erythema infectiosum (ICD 057.0)

Often non-febrile, no constitutional symptoms, erythema on the cheeks and limbs, possibly recurrent. Probably viral. Occurrence: children 4-14 years old; household and school outbreaks. Control: isolation not required.


See Leishmaniasis, cutaneous.

Fascioliasis (ICD 121.3)

Abdominal pain (right upper quadrant), eosinophilia, biliary colic, jaundice. Caused by Fasciola hepatica, a trematode. Laboratory: eggs in the faeces or duodenal aspirate. Incubation: 10-60 days. Transmission: eating uncooked infested aquatic plants such as watercress. Reservoir: sheep and cattle. Occurrence: worldwide. Control: avoid eating uncooked aquatic plants in endemic areas.

Fasciolopsiasis (ICD 121.4)

Diarrhoea, constipation, vomiting, anorexia, eosinophilia. Massive infections may cause oedemas and intestinal obstruction. Caused by a trematode, Fasciolopsis buski. Laboratory: eggs in faeces. Incubation period: about 1 month. Transmission: eating uncooked, infested, aquatic plants. Occurrence: Asia. Control: avoid eating uncooked aquatic plants in endemic areas.

Fifth disease

See Erythema infectiosum.

Filariasis (ICD 125.9)

Early acute manifestations: fever, lymphadenitis, lymphangitis (many infected persons show no clinical symptoms). Complication: elephantiasis. Caused by nematodes Wuchereria bancrofti or Brugia malayi, which develop in lymphatics. Laboratory: eosinophilia; circulating microfilariae often difficult to see in spite of repeated examinations day and night. Incubation: 3 months or longer. Transmission: by bite of vector mosquito, belonging to Culex, Aedes, Anopheles and Mansonia genera, depending on local prevalence; no direct person-to-person transmission. Occurrence: warm and humid tropical climates. Control: treatment with diethylcarbamazine, vector control, mass treatment of carriers. Reference: WHO Technical Report Series, No. 702, 1984 (Fourth report of the WHO Expert Committee on Filariasis).

Five-day fever

See Trench fever.

Flea-borne typhus

See Typhus fever due to Rickettsia typhi.

Food poisoning

(1) Bacillus cereus food poisoning (ICD 005.8)

Sudden onset, vomiting only (heat-stable toxin), or diarrhoea and abdominal cramps (heat-labile toxin). Rarely fatal. Caused by the enterotoxin of Bacillus cereus. Laboratory: identification of the agent in stools and in the suspect food (counting of bacteria on selective media). Incubation: vomiting type, 1-6 hours; diarrhoeal type, 6-16 hours. Transmission: rice, vegetables and meat contaminated with spores from soil and kept at ambient temperature after cooking, permitting multiplication of the organism; no person-to-person transmission. Occurrence: mainly in Europe. Control: adequate cooking and preservation of food.

(2) Botulism

(a) Food poisoning (ICD 005.1)

Acute onset, double vision, dryness of the mouth, sore throat, vomiting, diarrhoea, cranial-nerve paralysis, descending paralysis, and respiratory failure. One-third of patients may die in 3-7 days as a result of respiratory failure. Caused by toxins secreted by different types of Clostridium botulinum, a bacterium. Laboratory: demonstration of specific toxin in serum or stool; identification of organisms in suspect food. Incubation: 12-36 hours or several days. Transmission: home-canned vegetables and fruits contaminated by spores contained in soil, preserved or smoked meats and fish. Toxin is destroyed by boiling, but spores are resistant. No person-to-person transmission.

Refrigeration does not necessarily prevent toxin production. Occurrence: worldwide; common-source infection. Control: polyvalent antitoxin or monovalent if the bacillus has been typed, detection of one case and identification of source should encourage a search for other possible cases.

(b) Botulism of infants

Progressive onset, constipation, lethargy and paralytic signs as above, with a wide spectrum of severity; case fatality rate: treated, 3%; untreated much higher. The disease results from colonization of the intestine by C. botulinum and production of various toxins. Laboratory: identification of bacillus and/or toxin in faeces or autopsy specimens. Incubation: duration unknown. Transmission: honey has been incriminated, no person-to-person transmission. Occurrence: probably worldwide, not well documented, mainly infants under 1 year of age. Control: as in (a) above.

(3) Clostridium perfringens food poisoning (ICD 005.2)

Caused by the toxins of several serotypes of Clostridium perfringens, an anaerobic bacillus. Type A: abdominal pain, diarrhoea, benign prognosis. Type C: necrotizing enteritis, severe prognosis. Laboratory: semiquantitative anaerobic culture of stools and suspect food (heavy bacterial contamination is required for clinical disease). Incubation: 6-24 hours, usually 10-12 hours. Transmission: beef, pork, turkey or chicken contaminated with faeces or soil containing spores, which germinate during cooking at moderate temperature and on rewarming; no person-to-person transmission. Occurrence: worldwide; outbreaks originate in food-catering firms and restaurants where cooking and refrigeration are inadequate. Treatment: fluid replacement when indicated. Control: only preventive, with special attention to meat, which should be served as soon as it is cooked, or rapidly refrigerated after cooking, and thoroughly reheated, if necessary.

(4) Staphylococcal food poisoning (ICD 005.0)

Violent onset, severe nausea and vomiting, cramps, watery diarrhoea, prostration, low blood pressure, mild or no fever. Short-duration disease, fatality rare. Caused by enterotoxins secreted by certain strains of Staphylococcus aureus. Laboratory: isolation of toxin-producing Staphylococcus in vomit, faeces or suspect food; their absence does not rule out this etiology if the outbreak has characteristic features. Incubation: 1-6 hours, usually 2-4 hours. Transmission: wide variety of food processed by Staphylococcus carriers (finger and eye infections, nasal secretions, apparently normal skin), ham, pressed meat, milk from cows with infected udders; no person-to-person transmission. Occurrence: worldwide, relatively frequent. Control: symptomatic treatment, investigation of source of infection. Prevention: prompt and correct refrigeration of processed food, exclusion of infected food handlers.

(5) Vibrio parahaemolyticus food poisoning (ICD 005.4)

Watery diarrhoea, abdominal cramps with vomiting, fever and headache usually present; occasionally a dysentery-like illness with blood and mucus in stools and high fever. Usually non-fatal. Caused by a bacterium, Vibrio parahaemolyticus. Laboratory: isolation of organisms from stools on special media. Incubation: 4-96 hours, usually 12-24 hours. Transmission: raw or insufficiently cooked seafood (the organism can survive at 80°C for 15 minutes) followed by storage at ambient temperature; no person-to-person transmission. Occurrence: worldwide; sporadic cases or common-source outbreaks. Control: adequate cooking.

(6) Other agents of food poisoning (ICD 005.9)

These include chemical contaminants and organic substances that may be present in certain foods, such as mushrooms, fish, shellfish, and various fruits and vegetables. Mushroom poisoning may be caused by muscarine (onset in few minutes to 2 hours, salivation, sweating, vomiting, cramps, diarrhoea, confusion, coma), or phalloidine (onset 6-24 hours, same gastrointestinal symptoms plus oliguria, jaundice, liver damage), both of which have a severe prognosis. Among several agents of fish poisoning, icthyosarcotoxism due to ciguatera results from eating fish containing a toxin produced by a marine dinoflagellate of coral reefs in tropical seas. After hours, this may cause a common-source-type outbreak characterized by circumoral tingling, vomiting, diarrhoea, generalized pains, fever, prostration and paralysis. Shellfish poisoning by mussels and clams that have ingested poisonous dinoflagellates may cause similar symptoms, 5-30 minutes after eating. Certain oysters may cause gastrointestinal symptoms, bleeding, and liver disturbances, which appear 24-48 hours after ingestion and have a severe prognosis. Chemical poisoning may result from the presence of toxic insecticides on fruit and vegetables, use of lead-glazed pottery, etc. Reference: HALSTEAD, B. W. & SCHANTZ, E. J. Paralytic shellfish poisoning. Geneva, World Health Organization, 1984 (WHO Offset Publication, No. 79).

Gammaherpesviral mononucleosis (ICD 075)

Onset with grippe-like malaise followed by high fever, sore throat (exudative pharyngitis), localized posterior cervical or generalized adenopathy, splenomegaly (50% of cases), hepatomegaly (20%), jaundice (5%), orbital oedema, or typhoidal form without sore throat (10%). Complications: pneumonitis, meningoencephalitis; hepatic sequelae are unusual. Caused by human (gamma) herpesvirus 4 (“Epstein-Barr virus”) (family Herpesviridae). Differential diagnosis: streptococcal pharyngitis, diphtheria, necrotizing ulcerative pharyngitis, rubella, adenovirus infection, hepatitis, toxoplasmosis, cytomegalovirus infection. Laboratory: elevated total white blood cell count by the 2nd-3rd week with lymphocytosis and atypical lymphocytes (occasionally found in viral hepatitis, measles, rubella); heterophil antibody (Paul-Bunnell-Davidsohn test) appears by the 2nd week of illness (may be absent in children and 10% of adults). Incubation: 4-6 weeks. Transmission: direct by oral route (saliva), indirect by blood transfusion; excretion may persist for months. Occurrence: worldwide, during early childhood in areas of poor hygiene, during adolescence in higher socioeconomic groups; not very contagious, outbreaks in closed communities (colleges, universities, military groups). Control: no specific treatment; no isolation; safe disposal of nose and throat discharges.

Gastroenteritis, viral

See Acute viral gastroenteropathy and Rotaviral enteritis.

Giardiasis (ICD 007.1)

Chronic diarrhoea, greasy malodorous stools, abdominal cramps, fatigue. Caused by Giardia lamblia a flagellate protozoon. Laboratory: identification of cysts or trophozoites in serial examination of stools. Incubation: 2 weeks (range 1-4 weeks). Transmission: faecal-oral, person-to-person, contaminated water supplies (the cysts withstand chlorination), food, frequent asymptomatic carriers. Occurrence: worldwide, children and adults, localized common-source outbreaks. Control: treatment with mepacrine hydrochloride, investigation of source of infection; control of water supplies; personal hygiene and community sanitation: excreta precautions. Reference: WHO SCIENTIFIC WORKING GROUP. Parasite-related diarrhoeas. Bulletin of the World Health Organization, 58: 819-830 (1980).

Glandular fever

See Gammaherpesviral mononucleosis.

Guillain-Barré syndrome (ICD 357.0)

Progressive ascending symmetrical peripheral paralysis of the limbs which may reach the face and trunk, with sensorial alterations but without febrile syndrome. Recovery without sequelae after a period of 2-3 weeks. Rare complication: respiratory paralysis. Very low fatality rate. Laboratory: no cells in cerebrospinal fluid and high protein content (albuminocytological dissociation). No specific agent, rather a complication of recognized or unrecognized viral infections and immunization with viral vaccines 1-3 weeks earlier. No person-to-person transmission. Occurrence: adults, probably worldwide but not documented everywhere. Control: symptomatic treatment.

Guinea-worm disease

See Dracontiasis.

Haemorrhagic conjunctivitis, epidemic

See Enteroviral haemorrhagic conjunctivitis.

Haemorrhagic fever with renal syndrome (ICD 078.0)

Severe form: sudden onset with fever, headache, lethargy, abdominal and lumbar pain, facial flush, injection of the conjunctiva, petechiae. Proteinuria appears on 3rd-5th day, followed on 5th day by hypotensive phase, confusion, delirium, coma, ecchymoses, haemoptysis, haematemesis, haematuria, steep fall in platelets. Oliguric phase over the next 3-4 days, followed by a diuretic phase with risk of hypotension and shock, pulmonary oedema, severe electrolytic imbalance. Mild form: abrupt onset, after 3-6 days backache and abdominal pain are predominant, proteinuria, oliguria, moderate thrombocytopenia. Case fatality rate: untreated 15%, treated 5%, mild form 0.5%. Inapparent infection exists. Caused by Hantaan virus (family Bunyaviridae). Laboratory: safety precautions, isolation of virus from blood difficult, serological test. Incubation: 7-35 days, usually 14-21. Transmission: rodent excrement, field rats in rural areas, Rattus norvegicus in urban areas, laboratory rats; no person-to-person transmission. Occurrence: severe form in east Asia, mild form in Scandinavia and possibly in other parts of the world; seasonal, adults, rural foci. Control: no specific treatment; gown, gloves and mask isolation; disinfection of blood-contaminated discharges: rodent control; no international measures but information desirable. Reference: Haemorrhagic fever with renal syndrome: Memorandum from a WHO meeting. Bulletin of the World Health Organization, 61: 269-275 (1983); WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Hand, foot and mouth disease

See Enteroviral vesicular stomatitis with exanthem.

Heatstroke-heat exhaustion (ICD 992.0)

Both may mimic outbreaks of infectious disease. Heat stroke: hot, red, dry skin, little sweating (key sign), hard rapid pulse, very high temperature, unconsciousness and convulsions. Heat exhaustion: pale, greyish, clammy skin, weak and slow pulse, low blood pressure and faintness, shock. Treatment of heat stroke: emergency cooling by wrapping in wet cloths or immersing in cool water. Treatment of heat exhaustion: as for syncope, head down, replace lost salt and water orally.

Hepatitis, viral

See Viral hepatitis.


See Enteroviral vesicular pharyngitis.

Herpesviral gingivostomatitis (ICD 054.2)

Deep and painful vesicles and ulcers in the mouth, fever and malaise. Fatality rate low. Complications: keratoconjunctivitis, meningoencephalitis. Caused by type 1 herpesvirus. Incubation: 2-12 days. Transmission: direct contact with pharyngeal secretions; asymptomatic carriers. Occurrence: worldwide, usually an asymptomatic primary infection of young children but outbreaks may occur in closed communities. Control: personal hygiene, drugs being evaluated; secretion precautions.

Histoplasmosis (ICD 115.9)

Pulmonary form of a systemic mycotic infection easily overlooked, fever, malaise, mild respiratory illness, chest pain, cough, dyspnoea, occasionally more severe systemic and pulmonary symptoms, X-rays show pulmonary infiltrates and enlarged hilar lymph nodes. Complications: chronicity. Caused by a fungus, Histoplasma capsulatum. Laboratory: Giemsa staining of sputum, histoplasmin reaction, complement-fixation test. Incubation: 5-18 days, usually 10 days. Transmission: airborne, no person-to-person transmission. Occurrence: foci in the Americas, eastern Asia, Europe and Africa (a different variety of the fungus); outbreaks in groups of workers exposed to infected birds and bats or their droppings. Control: amphotericin B.


See Food poisoning, other agents.

Infectious mononucleosis

See Gammaherpesviral mononucleosis.

Influenza (ICD 487.1)

Sudden onset, chills, fever, headache, generalized aches, prostration, coryza, sore throat, severe and protracted cough, duration 2-7 days. Complications: bronchitis, bronchiolitis, pneumonitis, secondary bacterial pneumonia. Caused by influenza viruses A and B. Laboratory: isolation of virus from nasopharyngeal aspirate or throat swabbing, serotyping of strain in WHO collaborating centres; serological tests. Incubation: 24-72 hours. Transmission: droplets, aerosols, nasal discharges. Occurrence: in winter, worldwide, outbreaks of influenza A occur annually, major epidemics at intervals of 2-3 years and pandemics (up to 15-40% attack rate) at intervals of about 10-15 years. Influenza B occurs annually with epidemics at intervals of 4-7 years, with high incidence in closed communities (e.g., nursing homes for the elderly). Control: immunization with vaccine adapted to current A and B variants in advance of the epidemic season, particularly for personnel of public services, the elderly and immunocompromised persons (with inactivated vaccine); rimantadine as preventive drug after contact or to alleviate infection (ineffective against influenza B); secondary pneumonias require RESPIRATORY ISOLATION or STRICT ISOLATION. Notification of epidemics to WHO (disease under surveillance). Reference: periodic information on outbreaks, occurrence of variant strains and recommended composition of vaccines is published in the Weekly epidemiological record.

Japanese encephalitis

See Arthropod-borne viral encephalitides.

Junin and Machupo haemorrhagic fevers (ICD 078.7)

The two diseases are very similar although caused by two different arenaviruses. Insidious onset, moderate fever, generalized aches and, after a few days, haemorrhages from the gums and nose, haematemesis, haematuria and melaena. Case-fatality rate varies from 5% to 30% death may result from hypovolaemic shock. Laboratory: safety precautions, isolation of virus and serological tests. Incubation: 7-16 days. Transmission: excreta of infective rodents (Calomys spp.) contaminating dust and foodstuff’s; a few instances of person-to-person transmission for Machupo haemorrhagic fever. Occurrence: seasonal, mainly in adults in limited rural foci in Argentina and Bolivia. Treatment: immune serum or globulin. Control: rodent control. References: Argentine haemorrhagic fever surveillance. Weekly epidemiological record, 57: 219-220 (1982); WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Kala azar

See Leishmaniasis, visceral.

Katayama fever

See Acute schistosomiasis.

Kawasaki syndrome

See Mucocutaneous lymph node syndrome.

Keratoconjunctivitis, epidemic

See Adenoviral conjunctivitis.

Korean haemorrhagic fever

See Haemorrhagic fever with renal syndrome.

Kyasanur Forest disease (ICD 065.2)

Clinically similar to Omsk haemorrhagic fever with more frequent meningoencephalitis. Caused by a flavivirus. Incubation: 3-7 days. Transmission: cattle ticks, laboratory infections. Occurrence: only in Mysore State, India. Control: tick repellents, a vaccine is used locally. Reference: WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Laryngotracheobronchitis (ICD 466.0)

Fever, cough, stridor, respiratory distress. Caused by parainfluenza viruses, respiratory syncytial virus and influenza virus. Incubation: few days to a week. Transmission: oral contact, droplets, articles freshly soiled with respiratory discharges. Occurrence: worldwide, cold season, high incidence in infants and preschool children; sometimes sharp outbreaks. Control: secretion precautions, no specific drug, unless diphtheria is a possibility, oxygen, tracheostomy if necessary.

Lassa fever (ICD 078.8)

Progressive onset with intermittent spiking fever, headache, myalgia, vomiting, diarrhoea, chest and abdominal pain, oropharyngeal ulcers with greyish membranes, cervical adenopathy, swelling of face and neck. During the second week severe cases show oedema, pleural effusion, cardiac and renal failure, haemoconcentration, encephalopathy, haemorrhagic manifestations, and shock. Fatality rate: 36-67%. Mild forms and inapparent infections occur not infrequently in endemic areas. Differential diagnosis: diphtheria, typhoid. Caused by an arenavirus. Laboratory: safety precautions, isolation of virus from blood and the throat during the 1st and 2nd weeks, and from urine during the 2nd-5th weeks; serological tests (maximum-containment laboratory). Incubation: 7-21 days. Transmission: from field and semidomestic rodents (the multimammate rat, Mastomys natalensis) to man through contamination of food by urine, or dust; person-to-person contamination through blood, respiratory droplets and aerosols, more frequently by primary cases than by secondary ones. Occurrence: West and Central Africa. Treatment: immune plasma and antiviral drugs are presumed beneficial, intensive supportive care. Control: STRICT ISOLATION, surveillance of contacts; rodent control. References: MONATH, T. P. Lassa fever and Marburg virus disease. WHO Chronicle, 28: 212-219 (1974); International symposium on arenaviral infections of public health importance. Bulletin of the World Health Organization, 52: 381-766 (1975); Lassa fever. Weekly epidemiological record, 49: 341-343 (1974); WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Legionnaires’ disease (ICD 482.8)

Insidious onset, low-grade fever for 5 days then sudden rise in temperature with chills, diarrhoea, cough, chest or abdominal pain; X-rays show nodular then lobar consolidation; occasional extra-pulmonary manifestations such as diarrhoea, encephalopathy, hepatic and renal dysfunction. Complications: hypoxaemia, renal failure, shock. Fatality rate: 15-20%. Differential diagnosis: other pneumonias. Caused by a bacillus, Legionella pneumophila serotype 1. Laboratory: safety precautions, visualization of agent by immunofluorescence, cultivation, serological tests by immunofluorescence; IgM antibody remains high for at least 18 months after clinical infection. Incubation: 2-10 days, usually 5-6. Transmission: infected water supplies and air-conditioning systems, dust from excavation works, aerosol spread, no person-to-person transmission yet documented. Occurrence: worldwide, middle and older age groups, sporadic or epidemic, common-source infections. Control: erythromycin intravenously and rifampicin; gown, secretion precautions; identification of source of exposure and disinfection. Reference: REID, D. ET AL. Illness associated with “package tours”: a combined Spanish-Scottish study. Bulletin of the World Health Organization, 56: 117-122 (1978).

Leishmaniasis, cutaneous (ICD 085.9)

Two forms: oriental sore, characterized by single or multiple ulcerating skin lesions, and espundia with same cutaneous lesions and mutilating ulcerative lesions of the nose and pharynx. Oriental sore is caused by Leishmania tropica, a protozoan parasite of histiocytes, and espundia by L. braziliensis and L. mexicana. Laboratory: non-flagellated forms of the parasite may be seen by microscopic examination of stained smears or scrapings from the edges of lesions and this material may be cultivated in special media. Incubation period: from a few days to several months. Infectious period: until healing of lesions. Transmission: bites of phlebotomines (sandflies) infected by feeding on wild rodents and dogs; no direct person-to-person transmission. Occurrence: oriental sore in Africa (except South Africa), south-west Asia, China, India, and the Mediterranean basin; American leishmaniasis is restricted to tropical forests. Control: indoor application of residual insecticides, elimination of breeding sites (rubbish heaps), use of repellents and fine mesh screens; treatment with specific drugs. Reference: WHO Technical Report Series, No. 701, 1984 (The leishmaniases: report of a WHO Expert Committee).

Leishmaniasis, visceral (ICD 085.0)

Gradual or sudden onset of fever with continued and irregular course, lymphadenopathy, hepatosplenomegaly, anaemia and leukopenia. Untreated, usually fatal chronic course. Caused by Leishmania donovani, a protozoan parasite of histiocytes. Laboratory: demonstration of parasite in stained smears of lymph nodes, bone marrow or blood. Incubation: 10 days to 2 years, usually 2-4 months. Transmission: from dogs, cats and rodents to man, or from man to man through the bite of sandflies (phlebotomines). Occurrence: rural areas of tropical and subtropical regions; scattered cases or occasionally limited outbreaks. Control: treatment with specific drugs, vector control, protection from bites of phlebotomines. Reference: WHO Technical Report Series, No. 701, 1984 (The leishmaniases: report of a WHO Expert Committee).

Leptospirosis (ICD 100.9)

Abrupt onset, fever, headache, vomiting, muscular aches, conjunctivitis and occasionally rash. Complications (during second phase): jaundice, meningitis, haemorrhages in the skin and mucous membranes; and renal failure. Fatality rate: from low up to 20%. Caused by several serotypes of Leptospira (spirochaetes). Differential diagnosis: influenza, other causes of meningitis and hepatitis. Laboratory: isolation of leptospires from blood during the acute illness, from urine after the first week; rising titres in serological tests. Incubation: 4-19 days, usually 10. Transmission: direct contact with infected domestic animals, rodents, wild animals or contaminated water; penetration of leptospires through skin abrasions or mucous membranes. Occurrence: worldwide, urban and rural outbreaks, field workers with hazardous occupations, or recreational hazard. Control: antibiotics, search for source of infection; excretion precautions (urine). Reference: Guidelines for the control of leptospirosis, Geneva, World Health Organization, 1982 (Offset Publication, No. 67).

Listeriosis (ICD 027.0)

Sudden onset, fever, headache, nausea, vomiting, signs of meningeal irritation, delirium, coma, occasionally shock. Caused by Listeria monocytogenes, a bacterium. Laboratory: cerebrospinal fluid may be turbid (at beginning) or purulent. Incubation: 4 days to 3 weeks. Transmission: largely neonatal or possibly venereal but also by contact with soil contaminated by animal faeces, contaminated food, and inhalation. Occurrence: worldwide, usually sporadic but small epidemics may occur. Control: precautions in handling aborted animal fetuses; antibiotics; secretion precautions.

Lyme disease

See Erythema chronicum migrans due to Borrelia burgdorferi.

Lymphocytic choriomeningitis (ICD 049.0)

Onset as for influenza, or directly with meningeal signs and symptoms; possible meningoencephalomyelitis and coma but followed by recovery without sequelae. Caused by lymphocytic choriomeningitis virus. Laboratory: isolation of virus from blood or spinal fluid. Incubation period: 8-13 days for systemic symptoms, 15-21 days for meningeal symptoms. Transmission: food or dust contaminated by urine of infected rodents, usually mice; no person-to-person transmission. Occurrence: worldwide, usually sporadic; hamster pets have caused outbreaks. Control: isolation is not necessary; disinfection of discharges recommended.

Machupo haemorrhagic fever

See Junin and Machupo haemorrhagic fevers.

Malaria (ICD 084.9)

Classical symptoms may be preceded by 2-3 days of low-grade fever and malaise, often misidentified as influenza. Falciparum malaria (caused by Plasmodium falciparum), is life-threatening, presents with fever, chills, sweats, and headache and may progress to recurrent attacks or suddenly to disorientation, acute encephalitis, delirium and coma (cerebral malaria) or shock with high case-fatality rate. Malaria caused by Plasmodium vivax, P. ovale or P. malariae is less dangerous, except in the very young; classical attack begins with malaise and shaking chills, followed by rapidly rising temperature with headache and nausea and ending with profuse sweating; attacks recur at fixed or varied intervals; relapses are common for several months. The clinical picture may be atypical in individuals taking inadequate doses of prophylactic drugs or partially immune after long residence in endemic areas. Differential diagnosis: septicaemia, relapsing fever, brucellosis, and several other febrile diseases. Laboratory: repeated thin and thick blood smears; identification of the Plasmodium type is useful for prognosis and therapy; double infection is a possibility. Incubation: averaging 12 days for P. falciparum, 14 days for P. vivax and 30 days for P. malariae, but some P. vivax strains in the northern hemisphere may have a much longer incubation period (6-9 months). Transmission: man is the reservoir; different species of Anopheles mosquito, the great majority of which bite at night, acquire the infection and become infective after a temperature-dependent incubation period; occasional transmission through the placenta or by blood transfusion. Occurrence: in endemic tropical and subtropical areas (see Fig. A3.1); all age groups; commonly increasing attack rate during the rainy season; outbreaks may be explosive in non-immune groups not protected by prophylactic drugs. Control: treatment and prophylaxis require different drugs depending on drug resistance of parasites, particularly P. falciparum (see Table A3.1). Chloroquine resistance is widespread, and resistance to sulfadoxine-pyrimethamine is becoming a problem. WHO publishes information periodically in the Weekly epidemiological record on areas where resistance has appeared. Other measures include: isolation of patients under bed-nets at night; vector control in the community e.g., residual spraying, larviciding, source reduction; individual measures, e.g., the screening of openings of dwellings, bed-nets (may be impregnated with insecticide), staying indoors from dusk to dawn, wearing long-sleeved clothing and trousers after dusk, repeated application of repellents, use of mosquito coils. Notification to national authorities and WHO (disease under surveillance). References: Malaria risk in international travel. Weekly epidemiological record, 59: 221-227, 229-235, 237-240 (1984); Malaria chemoprophylaxis. Weekly epidemiological record; 60: 181-183 (1985); WHO Technical Report Series, No. 711, 1984 (Advances in malaria chemotherapy: report of a WHO Scientific Group); WHO Technical Report Series, No. 735, 1986 (WHO Expert Committee on Malaria: 18th report).

Fig. A3.1. Epidemiological assessment of status of malaria 1984

WHO 851686

Table A3.1. Treatment and prophylaxis of malariaa

P. vivax, P. ovale, P. malariae, and non-resistant P. falciparum

P. falciparum resistant to chloroquine

P. falciparum resistant to chloroquine and to sulfadoxine-pyrimethamine

Treatment of moderate attack

Chloroquine or amodiaquine,b orally

Sulfadoxine-pyrimethamine, orally

Quinine + tetracyclinec orally

Treatment of severe attack (P. falciparum)

Quinine (or chloroquine), intravenously

Quinine, intravenously

Quinine, intravenously


Chloroquine or amodiaquine, orally (should be continued for 4-6 weeks after exposure)

Amodiaquined orally

Amodiaquine,d orally

a This table can only give general indications: for further details, including contraindications, see references mentioned in text.

b In addition, primaquine is used against hepatic stages of P. vivax.

c A new drug, mefloquine, is active against resistant strains but resistance to it may develop: it is not recommended for mass prophylaxis; it is recommended to associate It with sulfadoxine-pyrimethamine for treatment.

d Sulfadoxine-pyrimethamine is not recommended for prophylaxis, because of its toxicity; amodiaquine does not offer full protection, and special care should be taken to avoid being bitten by mosquitos. Prompt diagnosis and treatment of breakthroughs are important.

Marburg virus disease

See Ebola and Marburg virus diseases.

Measles (ICD 055.9)

Onset with moderate fever, coryza, conjunctivitis, bronchitis, occasionally white Koplik’s spots on the buccal mucosa opposite the first and second upper molars (2nd-4th day). On 3rd-7th day: high fever, macular or maculopapular rash spreading rapidly from the face to the trunk and extremities; petechiae and ecchymoses may be present in severe cases. Complications: otitis media, pneumonia (infants), encephalitis (1 in 2000 cases) 2 days to 3 weeks after onset of rash. Particularly severe in malnourished children (fatality rate 10%): haemorrhagic (black) measles, mouth sores, dehydration, protein-losing enteropathy, kwashiorkor, skin infection. Congenital malformations in pregnant women. Caused by measles virus, a paramyxovirus. Differential diagnosis: rubella, scarlet fever, roseola infantum, gammaherpesviral mononucleosis, echovirus and coxsackievirus exanthems. Laboratory: the clinical diagnosis is obvious during epidemics; if necessary, serological test for detection of IgM antibody. Incubation: 10 days (range 8-13). Transmission: direct, by droplets and airborne droplet nuclei (aerosols), from 2-4 days before onset of the rash until 4 days after; indirect (unusual) by soiled articles; products of desquamation are not infectious. Occurrence: epidemics every 2 or 3 years in late winter and early spring; mainly affects children between 6 months and 3 years of age in developing countries, older children in developed countries or even nonimmunized young adults; outbreaks may be explosive. Control: no specific treatment, the immunoglobulin is ineffective in complications; RESPIRATORY ISOLATION for 7 days after onset of rash; no disinfection; immunization of contacts within 2 days of exposure can protect (if vaccine is contraindicated, immune globulin should be given within 3-4 days of exposure). Prompt immunization at the beginning of an epidemic is essential to limit the spread and immunization should be a requirement for school attendance. Live attenuated vaccine is given in a single injection at 12-15 months of age in developed countries, and at 9 months of age in countries with high incidence. Storage of vaccine at 2-8°C. Slight fever and malaise may occur in 5-30% of those vaccinated (contraindicated in pregnant women). Reference: Optimal age for measles vaccination in high incidence countries. Weekly epidemiological record, 57: 89-96 (1982).

Melioidosis, pulmonary (ICD 025)

Progressive onset, irregular fever, chest pains, X-rays show pulmonary consolidation with cavitating aspects. Complications: septicaemia (rapidly fatal), abscesses (including brain). Caused by a bacterium, Pseudomonas pseudomallei (Whitmore bacillus). Laboratory: Gram staining, isolation of the agent, serological tests. Incubation: from 2 days to several months. Transmission: common-source exposure by contact with soil, dust, water or mud through skin wounds, or ingestion of water contaminated by animal reservoirs; no person-to-person transmission. Occurrence: limited foci in all continents, mainly in warm climates. Control: chloramphenicol, tetracyclines; secretion precautions.

Meningitis due to Haemophilus influenzae (ICD 320.0)

Sudden onset, fever, vomiting, lethargy, meningeal irritation. Caused by Haemophilus influenzae, a bacillus. Laboratory: isolation of agent from blood or cerebrospinal fluid. Incubation period: 2-4 days. Infective period: during presence of agent in pharynx; may be prolonged. Transmission: droplets and nasopharyngeal discharges. Occurrence: mainly children below 5 years of age, worldwide, secondary cases in families and day-care centres. Control: isolation not necessary; treatment of patients with antibiotics.

Meningitis, viral (ICD 321.7)

Sudden onset, fever, malaise, headache, vomiting, stiff neck and back; maculopapular, vesicular or petechial rash may occur; may be associated with gastrointestinal and respiratory symptoms. Usually non-fatal, occasionally temporary residual weakness and muscle spasms. Caused by different viruses, most frequently mumps virus, coxsackievirus B, echovirus; less frequently poliovirus, coxsackievirus A, measles virus, herpesvirus, varicella virus, lymphocytic choriomeningitis virus, “Epstein-Barr virus”, influenza virus and adenoviruses, but the agent remains unidentified in 33% of cases. Differential diagnosis: postvaccinal meningitis, cryptococcal and other fungal meningitis, chlamydial lymphogranuloma, leptospirosis, listeriosis. See also Meningococcal meningitis and Meningoencephalitis due to miscellaneous infectious agents. Laboratory: cerebrospinal fluid clear with moderate mononuclear pleocytosis (sometimes polymorphonuclear at onset), increased protein, normal sugar and absence of bacteria; the etiological diagnosis is difficult and requires the isolation of the virus from blood, stool or throat washing with a rise of antibody in serum to confirm its pathogenic role. Incubation: varies with the specific agent (2 days to 1 week). Transmission: respiratory and/or faecal-oral. Occurrence: worldwide, occasionally in epidemics, seasonal increase in summer, higher frequency in warm climates. Control: personal, community, and food hygiene, excretion precautions. Prophylaxis: poliovirus vaccination; personal and food hygiene; community sanitation.

Meningococcal bacteraemia (ICD 036.2)

Fever, sudden prostration, petechial rash, ecchymoses, sometimes arthritis, shock; may occur without meningitis. High death rate. Caused by: Neisseria meningitidis, the meningococcus. Transmission: see Meningococcal meningitis. RESPIRATORY ISOLATION until 24 hours after start of chemotherapy.

Meningococcal meningitis (ICD 320.5)

Onset sudden with fever, intense headache, vomiting, stiff neck, and frequently petechial rash (rarely vesicles); delirium and coma often appear. Fulminating cases: sudden prostration, ecchymoses, with shock at onset. Fatality rates: untreated, 50%; treated, 10%. Caused by Neisseria meningitidis, several antigenic groups. Differential diagnosis: several bacteria may cause a similar disease (except for the rash), but more often sporadic than epidemic: pneumococci, Haemophilus influenzae, streptococci, Staphylococcus aureus, Escherichia coli. Salmonella, members of the Klebsiella-Enterobacter-Proteus group, Pseudomonas aeruginosa, Listeria monocytogenes and others. See also Meningitis, viral, and Meningoencephalitis due to miscellaneous infectious agents. Laboratory: turbid or purulent cerebrospinal fluid with polymorphonuclear pleocytosis, increased protein; demonstration of meningococci in Gram-stained smear of spinal fluid, isolation of the agent from the cerebrospinal fluid, characterization of group-specific meningococcal polysaccharides. Incubation: 2-10 days, usually 3-4 days. Transmission: direct contact, droplets, discharges from nose and throat, high prevalence of asymptomatic carriers (up to 50%). Contagiousness: as long as meningococci are present in nasopharynx. Occurrence: worldwide, greatest incidence during winter, epidemic waves at irregular intervals, large epidemics in tropical regions during hot dry season. Control: antibiotics (possible resistance to sulfonamides), RESPIRATORY ISOLATION until 24 hours after start of chemotherapy. Prevention: chemoprophylaxis (contacts in closed community), vaccine. References: WHO Technical Report Series, No. 588, 1976 (Cerebrospinal meningitis control: report of a WHO Study Group); GALAZKA, A. Meningococcal disease and its control with meningococcal polysaccharide vaccines. Bulletin of the World Health Organization, 60: 1-7 (1982).

Meningoencephalitis due to miscellaneous infectious agents (ICD 323.9)

Postinfectious encephalitis may occur in measles 2 days to 3 weeks after onset of exanthem; while unusual in rubella and varicella, it may occur at the end of the disease or 1-2 weeks after.

Postvaccinal encephalitis may occur, but rarely, after vaccination against smallpox, yellow fever, rabies, whooping cough.

Other diseases: non-paralytic poliomyelitis, lymphocytic choriomeningitis, rabies, herpes, influenza, cat-scratch fever, and certain bacterial, enteroviral, leptospiral, parasitic (trypanosomiasis, cysticercosis, hydatidosis, gnathostomiasis) and mycotic infections.

Simian B virus disease is an ascending encephalomyelitis (only a few cases are known) transmitted by monkey bites, mostly in Africa and India (see Cercopithecid herpesvirus 1 disease).

Primary amoebic meningoencephalitis is characterized by fever, headache, vomiting, nuchal rigidity, somnolence, death in 5-6 days in fulminating forms; aseptic meningitis syndrome may also be seen. Caused by two amoebae, Acanthamoeba and Naegleria. Incubation: 3-7 days. Transmission: swimming in infected ponds, springs, swimming-pools. Occurrence: rare or undiagnosed, possibly worldwide, in warm season or warm climate. Control: treatment with amphotericin B, miconazole and rifampicin may be successful for Naegleria infection.

Monkeypox (ICD 051.9)

Clinically similar to smallpox, but caused by a different virus; case-fatality rate: 16%. Transmissions animal reservoir not well known, includes monkeys: secondary attack rate of about 10%. Occurrence: rain-forest areas of West and Central Africa. Control: STRICT ISOLATION; see Smallpox and Varicella.

Mononucleosis, infectious

See Gammaherpesviral mononucleosis.

Mucocutaneoos lymph node syndrome

A newly identified syndrome, fever lasting 5 days or more, maculopapular rash, bilateral conjunctival injection, oropharyngeal lesions, erythema and indurative oedema of the hands or feet, cervical lymphadenopathy. Complications: meningitis, arthritis, cardiac involvement; case-fatality rate 1%. Etiology unknown, may be a soluble immunocomplex disorder with a still unknown infectious agent. No usual laboratory test. Transmission: unknown, but not from person to person. Occurrence: outbreaks in children under 5 years of age in Japan and the USA; a few cases reported in Europe. No specific treatment.

Mumps (072.9)

Fever (may be absent), swelling and tenderness of salivary glands, usually the parotid. Complications: orchitis (20%), aseptic meningitis (frequent) or meningoencephalitis. Fatality: rare. Caused by mumps virus (genus Paramyxovirus). Differential diagnosis: in sporadic cases other causes of meningitis or meningoencephalitis are numerous but mumps is a frequent one. Laboratory: isolation of virus from saliva, blood, urine, cerebrospinal fluid; serological tests. Incubation: 2-3 weeks. Transmission: direct by person-to-person contact from 2 days before to 9 days after gland swelling, by droplet spread; about one-third of cases are inapparent but contagious. Occurrence: children, young adults; mainly in winter and spring; clusters of cases in households, schools, barracks, camps. Control: symptomatic treatment; disinfection of articles soiled with saliva; live attenuated vaccine may protect if administered shortly after exposure. RESPIRATORY ISOLATION for 9 days.

Murine typhus

See Typhus fever due to Rickettsia typhi.

Non-pneumonic Legionnaires’ disease (ICD 482.8)

Fever, chills, myalgia, malaise, headache, slight cough, chest pain or constricting sensations, no radiographic evidence of pulmonary disease, duration 2-5 days. Caused by Legionella pneumophila serotype 1. Differential diagnosis: influenza. Laboratory: safety precautions, visualization of agent by immunofluorescence, serological tests by immunofluorescence. Incubation: 5 hours-3 days, usually 1-2 days. Transmission: defective air-conditioning systems, no person-to-person transmission. Occurrence: a very small number of outbreaks have been documented in the USA, might be more widespread. Control: antibiotic treatment.

Omsk haemorrhagic fever (ICD 065.1)

Sudden onset with dengue-like symptoms. Acute phase: meningismus and haemorrhages. Caused by a flavivirus. Incubation: 3-7 days. Transmission: from infected rodents to man by ticks; laboratory infections; no person-to-person transmission. Occurrence: in Siberia, USSR. Control: protection from ticks by protective clothing and repellents; a vaccine is used locally. Reference: WHO Technical Report Series, No. 721, 1985 (Viral haemorrhagic fevers: report of a WHO Expert Committee).

Oriental sore

See Leishmaniasis, cutaneous.

Ornithosis (ICD 073)

Sudden onset, fever, headache, myalgia, chills, cough absent or non-productive at beginning, bronchopneumonia, splenomegaly; X-rays as in primary atypical pneumonia. Fatalities: rare. Caused by Chlamydia psittaci. Laboratory: safety precautions, isolation of chlamydia from blood or post mortem tissues; serological diagnosis by elevation of antibodies. Incubation: 4-15 days, usually 10 days. Transmission: contact with infected birds, mainly parrots, which may apparently be healthy, inhalation of desiccated droppings in enclosed space, laboratory infections, hospital infections. Occurrence: worldwide. Control: tetracyclines, search for source of infection; secretion precautions. Reference: Ornithosis/psittacosis surveillance. Weekly epidemiological record, 57: 1-4 (1982).

Oroya fever

See Bartonellosis.

Paragonimiasis (ICD 121.2)

Pulmonary symptoms and haemoptysis, simulates pulmonary tuberculosis radiologically; the brain, lymph nodes, and other organs may be involved. Caused by trematodes belonging to the genus Paragonimus. Laboratory: identification of eggs in sputum by microscope examination, also in faeces. Incubation period: eggs may appear 6 weeks after infestation but symptoms may be considerably delayed. Transmission: ingestion of uncooked freshwater crabs and crayfish in contaminated areas; no person-to-person transmission. Occurrence: Africa, Pacific coast of South America, Asia; small clusters of cases may occur. Control: food hygiene in endemic areas.

Paratyphoid fever (ICD 002.9)

Sudden onset, fever, diarrhoea, sometimes rose spots on the trunk, enlargement of the spleen. Fatality rate less than in typhoid fever. Caused by Salmonella paratyphi A, B and C. Laboratory: isolation of organism from blood and stools; serological tests. Incubation period: 1-10 days (shorter for gastroenteritis than enteric fever). Transmission: faecal-oral, food (meat, milk, eggs), food-handlers, flies, water, asymptomatic carriers. Occurrence: worldwide, all ages, sporadic, outbreaks in closed communities or clusters of cases from common source. Control: antibiotics, excretion precautions, search for source of infection, exclusion of infected persons from food handling. Vaccines have not proved effective.

Pertussis (ICD 033.9)

Insidious onset with cough which becomes characteristically paroxysmic within 1-2 weeks and lasts for 1-2 months. Fatalities occur mainly in infants under 1 year of age and in malnourished children. Differential diagnosis: adenovirus infection. Caused by a bacillus: Bordetella pertussis. Laboratory: cultivation of agent from throat swabs. Incubation: 7 days (maximum 21). Transmission: droplets are highly infectious before the paroxysmal cough stage; contagious period from 7 days after exposure to contact to 3 weeks after onset. Occurrence: epidemic, worldwide, mainly in infants and children, rarely in adults. Control: RESPIRATORY ISOLATION, disinfection of secretions; antibiotic treatment has little effect; prevention by vaccine or antibiotics given to contacts.

Phlebotomus fever

See Arthropod-borne viral fever.

Plague, bubonic (ICD 020.0)

Inguinal, axillary or cervical adenitis, rarely without fever. Complications: septicaemic plague (prostration, haemorrhages; 60% fatality rate if untreated-black death), pneumonic plague (highly contagious, lethal in 48 hours). Caused by a bacillus, Yersinia pestis. Laboratory: safety precautions, direct Gram staining and culture of fluid from buboes, blood, sputum. Incubation: 2-6 days. Transmission: bites of fleas of wild rodents in rural areas; bites of rat fleas (Xenopsylla cheopis), cat fleas and human fleas in urban plague; person-to-person transmission by airborne droplets and fomites in pneumonic plague. Occurrence: sylvatic plague with sporadic cases or small clusters in temperate and warm climates in areas with enzootic wild-rodent plague; urban plague with endemicity or epidemic peaks (domestic rat is a reservoir). Control: treatment with streptomycin, tetracyclines, chloramphenicol; skin precautions for bubonic plague; RESPIRATORY ISOLATION for suspected pneumonia in bubonic plague; disinfection of purulent discharges, sputum; terminal cleaning; strict aseptic precautions for corpses. Contacts: parasite disinfestation with insecticide effective against local fleas and surveillance for 7 days. Community measures: flea control must precede or coincide with anti-rodent measures. Prophylaxis: 3 injections of killed bacteria vaccine and periodic boosters. International measures: notification to WHO (disease subject to the International Health Regulations, which govern movements of ships and aircraft). References: Plague vaccine: Recommendations of the Immunization Practices Advisory Committee (IPAC). Weekly epidemiological record, 57: 332-334 (1982); BAHMANYAR, M. & CAVANAUGH, D. C. Plague manual. Geneva, World Health Organization, 1976.

Plague, pneumonic (ICD 020.5)

Sudden onset, high fever, chills, severe headache, cough develops in 24 hours, sputum at first mucoid then rusty or bright red, usually no signs of consolidation. Untreated: death within 48 hours. Differential diagnosis: pneumococcal and other bacterial pneumonias. Caused by Yersinia pestis, a bacillus. Laboratory: safety precautions, collection of sputum, Gram staining and culture on ordinary media. Incubation: 2-3 days. Transmission: highly transmissible by respiratory droplets and freshly soiled articles. Occurrence: as a complication of bubonic plague (see above) or as a primary infection. Control: STRICT ISOLATION; treatment: streptomycin, tetracyclines, chloramphenicol. Contacts: identification, isolation for 7 days, and chemoprophylaxis (including medical personnel); notification to WHO (disease subject to the International Health Regulations); other precautions as for bubonic plague.


See Epidemic myalgia.

Pneumonia, bacterial (ICD 482.9; 482.41)

1 For pneumonia due to Staphylococcus.

Fever, varying respiratory symptoms, X-rays showing various types of consolidation. Fatality rate may be high. Most often a complication of viral pulmonary infection. Caused by various bacteria: Staphylococcus aureus, Klebsiella pneumoniae, Haemophilus influenzae, Streptococcus pyogenes group A, coliform bacteria, Pseudomonas species, Escherichia coli, Francisella tularensis, Pseudomonas pseudomallei, Brucella abortus and Brucella melitensis. Incubation: 1-3 days. Transmission: respiratory droplet spread, articles freshly soiled with respiratory tract discharges. Occurrence: worldwide. Control: antibiotics, STRICT ISOLATION for staphylococcal infection and group A Streptococcus, secretion precautions for others.

Pneumonia due to Mycoplasma pneumoniae (ICD 483)

Gradual onset, fever, headache, malaise, paroxysmal cough, pharyngitis which progresses to bronchitis and pneumonia, X-rays show patchy infiltration. Duration: a few days to several weeks. Fatalities: rare. Caused by Mycoplasma pneumoniae. Differential diagnosis: pneumonitis caused by bacteria, adenovirus infection, influenza, parainfluenza, measles, Q fever, certain mycoses, tuberculosis. Laboratory: development of cold agglutinins (50% of cases); cultivation of agent on special media; serological tests. Incubation: 14-21 days. Transmission: aerial route. Occurrence: worldwide, schoolchildren and young adults, occasionally epidemics in institutions and military populations. Control: tetracyclines, secretion precautions.

Pneumonia due to Streptococcus pneumoniae (ICD 482.0)

Generally sudden onset, single shaking chill, high fever, pains in the chest, cough, dyspnoea, leukocytosis. After 3 days pulmonary symptoms are evident, rusty sputum, X-rays show a lobar consolidation. Fatality rate: 20-40% if untreated. Caused by Streptococcus pneumoniae (pneumococcus). Laboratory: Gram-positive diplococci in sputum, isolation of pneumococci from blood or sputum. Incubation: 1-3 days. Transmission: respiratory droplets, articles freshly soiled with respiratory discharges. Occurrence: worldwide, outbreaks in institutions (elderly persons), often secondary to viral pulmonary infection. Control: antibiotics, oxygen, secretion precautions, vaccination of high-risk groups (elderly).

Pneumonia due to other agents (ICD 486)

Pneumocystis carinii, a protozoon, endemic in America and Europe, possibly more widely spread, may cause outbreaks of acute or subacute pulmonary disease in infants in hospitals and institutions or opportunistic infections in adults, frequently associated with acquired immunodeficiency syndrome. Often fatal. Laboratory: visualization of the agent in smears of tracheobronchial mucus. Incubation: 1-2 months.

Coccidioides immitis, a fungus, extremely common in arid areas of the Americas, produces an asymptomatic infection or an overt influenza-like illness and progresses to mild limited pulmonary lesions or a generalized granulomatous disease. Highly lethal. Laboratory: microscopic examination and culture of sputum.

Chlamydia trachomatis may cause a distinctive pneumonitis syndrome in infants 4-24 weeks of age with cough, congestion, no fever, diffuse pulmonary involvement on chest X-ray, lasting a month or longer, with no fatalities. Transmission may be perinatal. Occurrence: may account for up to 30% of pneumonitis in infants admitted to hospitals; may occur in immunosuppressed persons.

Pneumonitis, viral (ICD 480.9)

Diffused interstitial pulmonary lesions, X-rays show increased hilar shadows or, at most, scattered small areas of consolidation. Complications: secondary bacterial pneumonia. May occasionally be fatal. Caused by various viruses: respiratory syncytial virus, and parainfluenza 3 virus in the first 6 months of life (may be responsible for “cot death”), measles virus, varicella virus in young children, adenoviruses types 3, 4 and 7 (acute respiratory disease has been seen in military recruits) and influenza virus at all ages. Laboratory: direct examination of rhinopharyngeal aspirates by immunofluorescence, isolation of agent by cell culture, which should be inoculated at bedside. Incubation: 1-3 days. Transmission: respiratory droplets, articles freshly soiled with respiratory discharges. Occurrence: worldwide, seasonal outbreaks, spreading easily in closed groups (military, nurseries). Control: secretion precautions; influenza and adenovirus vaccines.

Poliomyelitis (ICD 045.9)

Onset with moderate fever, headache, gastrointestinal disturbance, malaise, stiffness of the neck and back. After 2-3 days, sudden occurrence of flaccid asymmetrical paralysis without sensory loss, most commonly of the lower extremities. Minor illness (abortive poliomyelitis), aseptic meningitis, non-paralytic poliomyelitis and inapparent infections are frequent. Complications: lameness, ascending paralysis involving laryngeal and respiratory muscles, bulbar poliomyelitis. Fatality rate: 2-10%, more severe in adults. Caused by poliovirus types 1, 2, 3. Differential diagnosis: postinfectious polyneuritis, coxsackievirus and echovirus infections, tick-bite paralysis (uncommon), Guillain-Barré syndrome; non-paralytic poliomyelitis cannot be distinguished clinically from aseptic meningitis caused by echovirus and coxsackievirus, arboviruses, mumps virus, lymphocytic choriomeningitis virus, herpesvirus and leptospires. Laboratory: lymphocytes in cerebrospinal fluid (may be missing) and slight increase in protein content; isolation of the virus from faeces or oropharyngeal secretions, serological tests. Incubation: 3-35 days, usually 7-14. Transmission: throat secretions and faeces, asymptomatic carriers. Contagiousness: 7-10 days before and for a few days after the onset of symptoms. Occurrence: worldwide, still frequent in warm climates where it is endemic or epidemic in children. Control: no specific treatment, mechanical respiratory assistance if necessary, excretion (stool, urine) precautions for 7 days from onset. Control of epidemics by mass immunization with oral vaccine, monovalent if possible. Prophylaxis: oral live vaccine or inactivated vaccine in routine immunization programmes in infancy. Disease under surveillance by WHO. Reference: MELNICK, J. Advantages and disadvantages of killed and live poliomyelitis vaccines. Bulletin of the World Health Organization, 56: 21-38 (1978).

Pontiac fever

See Non-pneumonic Legionnaires’ disease.

Poxviral local cutaneous infections (ICD 051.9)

Fever and erythema may be present, the local lesion consists of vesicles or nodules, usually on a finger or hand. Caused by different poxviruses of animal origin: bovine papular stomatitis, contagious ecthyma (orf), cowpox (similar to vaccinia), goatpox, pseudocowpox, tanapox (Yaba pox). Differential diagnosis: cutaneous anthrax. Laboratory: safety precautions, electron microscopy of material from lesions, isolation of agent. Incubation: 1-2 weeks. Transmission: direct contact with animal lesions, occasionally indirect contact; tanapox may be arthropod-borne. Occurrence: worldwide, occupational, clusters of cases are possible. Control: skin precautions.


See Ornithosis.

Q fever (ICD 083.0)

Sudden chills, headache, fever, weakness, severe sweating, sore throat, chest pain, cough and pneumonitis signs. Fatality rate less than 1% Caused by a rickettsia, Coxiella burnetii. Laboratory: safety precautions, isolation of agent from blood; serological diagnosis by rise in specific antibodies in paired sera. Incubation: 2-3 weeks. Transmission: contact with infected animals, dust, contaminated material (e.g., wool, fertilizer, raw milk). Occurrence: worldwide, sporadic, veterinarians, explosive outbreaks in stockyards and animal industry. Control: tetracyclines, secretion precautions, search for source of infection, pasteurization of milk.

Queensland tick typhus

See Spotted fever group.

Rabies (ICD 071)

Progressive onset, fever, headache, mental depression, restlessness, paresis, sensorial symptoms, progressing to excitement, paralysis, painful spasms of the throat (hydrophobia, salivation), convulsions, delirium, death from generalized paralysis, asphyxia in 3-10 days. Usually fatal. Caused by rabies virus. Laboratory: staining of frozen skin specimens (occipital, retroauricular) or corneal impressions with fluorescent-labelled specific antibody; virus isolation in mouse or tissue culture; high antibody level in cerebrospinal fluid, from which the virus cannot be isolated. Incubation: 10 days to 1 year, usually 30-50 days. Transmission: bite of infected dogs or other domestic or wild animals, with or without symptoms; person-to-person transmission not confirmed. Occurrence: worldwide where infected animals are present. Control: secretion precautions (STRICT ISOLATION in some countries), symptomatic treatment. Prevention: postexposure active immunization, with or without immune globulin according to severity of risk, without delay after bite; pre-exposure vaccination for professionals at risk. Reference: WHO Technical Report Series, No. 709, 1984 (Seventh report of the WHO Expert Committee on Rabies).

Rat-bite fever (ICD 026.9)

May occur after the bite of an infected rat, even though wound healed normally. Sudden onset, general pains, maculopapular or petechial rash most marked on extremities. There are two separate etiological entities-streptobacillosis, caused by Streptobacillus moniliformis and spirillosis, caused by Spirillum minor. Laboratory: inoculation of blood, lymph node pus on special bacteriological medium. Incubation: 3-10 days. Transmission: rat bite or indirect contact with rats and contaminated food (milk), no person-to-person transmission. Occurrence: worldwide. Treatment: tetracyclines.

Relapsing fever (endemic, epidemic) (ICD 087.9)

Sudden onset, periods of fever during 2-9 days with general symptoms, relapses (2-10), possible delirium, transitory petechial rash during the initial period. Fatality rate: 2-10%. Caused by various species of the genus Borrelia. Differential diagnosis: malaria, dengue, yellow fever, leptospirosis, typhus, influenza and enteric fevers. Laboratory: spirochaetes seen in stained thick blood films or in dark-field preparations. Incubation: 5-15 days, usually 8 days. Transmission: in epidemic form, by crushing the body of an infected louse on to skin abrasion (the louse becomes infective 4-5 days after feeding on an infected person); in endemic form, by the bite of infected argasid ticks on vertebrate animals; no direct person-to-person transmission. Occurrence: epidemic louse-borne relapsing fever (due to B. recurrentis) in Africa, South America, Asia; endemic tick-borne relapsing fever (due to species other than B. recurrentis), with occasional outbreaks, in North and South America, central Asia, India, and the Mediterranean area. Control: delousing or tick control, tetracyclines. Treatment of louse-borne relapsing fever near the end of a paroxysm may cause the Herxheimer reaction, characterized by fever, headache, general malaise and rigors; it usually subsides after 1-2 hours, but can occasionally have sequelae such as hemiplegia or monoplegia. It can be prevented by administering prednisone before treatment. Louse-borne relapsing fever must be reported to WHO (disease under WHO surveillance).

Reye’s syndrome (ICD 331.8)

Fatty degeneration of brain and liver occurring on about the sixth day after upper respiratory tract or exanthematous viral infection, with vomiting, hepatic dysfunction, change in mental status, progressing rapidly in severe forms to coma and respiratory arrest, which may occur in 4 days. Gastrointestinal bleeding is possible. Transmission: not from person to person. Occurrence: children under 18 years of age, clusters of cases or outbreaks linked to influenza virus B, sporadic cases after varicella, enterovirus and myxovirus infections.

Rickettsialpox (ICD 083.2)

Initial skin lesion (eschar), varicelliform rash. Fatality rate less than 1%. Caused by Rickettsia akari. Incubation: 7-10 days. Transmitted by bite of an infective mouse mite, no person-to-person transmission. Occurrence: Africa, USA, USSR, probably other areas. Control: tetracyclines, elimination of house mice, miticides.

Rift Valley fever (ICD 006.3)

Dengue-like signs and symptoms with possible complications, such as haemorrhage, encephalitis and retinopathy. Caused by Rift Valley fever virus, a Bunyavirus. Differential diagnosis: dengue, yellow fever, other arthropod-borne viral fevers. Laboratory: safety precautions, isolation of virus from blood by mouse inoculation and cell culture; serological tests. Incubation: 2-7 days, usually 3. Transmission: mosquitos, mainly Culex genus, or direct contact with the blood of sick animals (sheep, cattle, camels); no documented person-to-person transmission. Occurrence: Africa south of the Sahara, Egypt. Control: insecticide spraying; vaccination of domestic animals (killed vaccine; live vaccine to be used only in outbreaks, after the virus has been identified); human vaccine still experimental and reserved for exposed professionals; patients to stay under bed-nets during acute phase. Reference: Rift Valley fever: an emerging human and animal problem. Geneva, World Health Organization, 1982 (WHO Offset Publication, No. 63).

Rocky Mountain spotted fever

See Spotted fever group.

Roseola infantum (ICD 057.8)

A disease of children. Sudden fever (40.5-41°C) of 3-5 days’ duration. Transient maculopapular rash appearing first on the trunk when the fever falls in lysis. Incubation: 5-15 days, usually 10 days. Probably viral.

Rotaviral enteritis (ICD 008.8)

Gastrointestinal symptoms may be preceded by respiratory illness (cough, nasal discharge) or otitis media (red throat, inflamed tympanic membrane). Vomiting generally starts before diarrhoea, which may cause severe dehydration and rapid circulatory collapse, particularly in children aged 12-18 months (usually less severe below 12 months); occasionally fatal; subclinical infections are frequent. Caused by rotaviruses, various serotypes. Laboratory: examination of stools by electron microscopy or enzyme-linked immunosorbent assay. Incubation: 2 days. Transmission: faecal-oral, infection through respiratory routes also seems possible. Occurrence: worldwide, sporadic, winter epidemics in temperate climates, less frequent and throughout the year in tropical climates. Control: rehydration, enteric precautions; investigation of contacts and source of infection.

Rubella (ICD 056.9)

Onset with moderate fever, occipital lymphadenopathy; occasional arthralgia; maculopapular rash on 3rd-5th day in 20-50% of cases, spreading from the face to the trunk and limbs, lasting 1-3 days. Prognosis generally benign. Complications: arthritis, encephalitis (rare), congenital malformations (infection during first trimester of pregnancy). Caused by rubella virus (family Togaviridae). Differential diagnosis: measles, scarlet fever, drug rashes, gammaherpesviral mononucleosis, erythema infectiosum, exanthema subitum, echovirus and coxsackievirus exanthems. Laboratory: isolation of virus during the first few days from blood, urine and faeces and for 2 weeks from the pharynx; serological test (fourfold rise in antibody titre in paired sera or presence of IgM in a single serum). Incubation: usually 16-18 days (range 14-21). Transmission: direct, by droplets from nose and throat and droplet nuclei (aerosols) from 1 week before onset of rash to 1 week after it has faded; infants born with congenital rubella excrete the virus for several months; indirect, through articles freshly soiled by nasopharyngeal secretions. Occurrence: major epidemics every 6-9 years in winter and spring, mainly a disease of childhood, less contagious than measles, clusters of cases in closed institutions (outbreaks have occurred in hospitals involving staff and patients). Control: no specific treatment; RESPIRATORY ISOLATION for 7 days from onset of rash; disinfection of articles freshly soiled; abortion should be considered for women who have had a possibly infective contact during early pregnancy; the value of immunoglobulin has not been established; mass immunization in schools or military groups, teachers and hospital staff. Prophylaxis by a single dose of live attenuated vaccine (contraindicated in pregnant women).

Salmonellosis (ICD 003.9)

Sudden onset, abdominal pain, fever, nausea, vomiting, diarrhoea, dehydration may be severe among infants. Complications: enteric fever, abscesses. Caused by the numerous serotypes of Salmonella. Laboratory: isolation of Salmonella from faeces. Incubation: 6-72 hours, usually 12-36 hours. Transmission: faecal-oral, person-to-person or common-source through food (meat, poultry, milk, dairy products, eggs and egg products), water, food-handlers. Occurrence: worldwide, sporadic cases, small outbreaks in the general population, large outbreaks in closed groups caused by contaminated food. Control: rehydration; use of antibiotics may lead to resistance; investigation of source and contacts; strict enteric precautions in hospitals, disinfection of faeces and soiled articles; community sanitation. Reference: WHO SCIENTIFIC WORKING GROUP. Enteric infections due to Campylobacter, Yersinia, Salmonella and Shigella. Bulletin of the World Health Organization. 58: 519-537 (1980). Salmonella and Shigella surveillance: Guidelines for bacteriological clearance of Salmonella and Shigella excreters. Weekly epidemiological record. 57: 156-158 (1982).

Sandfly fever

See Arthropod-borne viral fever.

Scarlet fever (ICD 034.1)

Sore throat, fever, vomiting, strawberry tongue, punctate rash that does not involve the face. Complications: otitis, rheumatic fever, glomerulonephritis. Fatality rate: 3% or less. Caused by Streptococcus pyogenes, group A. Laboratory: isolation of streptococci from throat and specific grouping of strains. Incubation: 1-3 days. Transmission: droplets, inapparent carriers are frequent. Occurs less frequently in tropical than in temperate climates. Affects the 3-12-year age group. Infective period: 10-21 days. Control: antibiotics, secretion precautions.

Schistosomiasis, intestinal (ICD 120.1)

For early manifestations, see Acute schistosomiasis. This is followed by intermittent diarrhoea with blood and mucus. Caused by intestinal infection with Schistosoma mansoni in tropical Africa and America, and the Mediterranean region, S. intercalatum in West Africa and S. japonicum in Asia. Incubation: 4-6 weeks. Laboratory: repeated microscopic examination of stools. Transmission: waters with infected snails. Reference: WHO Technical Report Series, No. 728, 1985 (The control of schistosomiasis: report of a WHO Expert Committee).

Schistosomiasis, urinary (ICD 120.0)

For early manifestations, see Acute schistosomiasis. This is followed by eosinophilia, lymphadenopathy, hepatosplenomegaly, cystitis and haematuria, which may be discrete. Bladder cancer may occur. Caused by Schistosoma haematobium, a trematode worm. Laboratory: identification of eggs by microscopic examination of urine; enzyme-linked immunosorbent assay. Incubation period: several weeks. Transmission: contact with contaminated water in endemic zones. Occurrence: Africa, Eastern Mediterranean area. Control: specific drugs for patients and molluscicides in contaminated waters. Reference: WHO Technical Report Series, No. 728, 1985 (The control of schistosomiasis: report of a WHO Expert Committee).

Shigellosis (ICD 004.9)

Fever, vomiting, abdominal pains, tenesmus, diarrhoea with mucus, pus and blood. Complications: septicaemia. Fatality rate may reach 20% if untreated. Caused by several serotypes of Shigella. Laboratory: isolation of Shigella from stools, which generally contain pus cells. Incubation: 1-7 days, usually 1-3. Transmission: faecal-oral, carriers with inapparent or mild infections, water, milk, flies. Occurrence: worldwide, all ages, higher severity in children under 10 years of age, frequent in warm climates, explosive outbreaks in closed groups. Control: antibiotics (there are resistant strains), rehydration, excreta precautions, disinfection of articles soiled by faeces, investigation of source and contacts, exclusion from food handling, pasteurization of dairy products, fly control. References: WHO SCIENTIFIC WORKING GROUP. Enteric infections due to Campylobacter, Yersinia. Salmonella and Shigella. Bulletin of the World Health Organization, 58: 519-537(1980); Shigella sonnei surveillance. Weekly epidemiological record, 57: 276-278 (1982).

Siberian tick typhus

See Spotted fever group.

Simian B virus disease

See Cercopithecid herpesvirus 1 disease

Sixth disease

See Roseola infantum.

Sleeping sickness

See Trypanosomiasis, African.

Smallpox (ICD 050.9)

See the description of variola major rash under Varicella; case-fatality rate: 20-40%. Variola minor has a similar rash but milder systemic symptoms and a case-fatality rate of 1%. Other forms include an attenuated disease with few lesions in partially immune persons, a fulminating haemorrhagic form, and “flat” smallpox with delayed appearance of lesions, which are superficial and do not leave scars. Caused by variola virus. Incubation: 7-17 days, usually 10-12. Transmission: airborne, respiratory droplets, contact with skin lesions, bedding and clothing. Contagiousness: until disappearance of all scabs, about 3 weeks. Control: STRICT ISOLATION of patients until all crusts are shed; intensive case-finding; vaccination of all categories of contacts, isolation of primary contacts (face-to-face contact with patient), medical surveillance of secondary contacts (contact with primary contact) and other possible remote contacts. STRICT SAFETY PRECAUTIONS for laboratory specimens (see Annex 4). Smallpox is now considered to have been eradicated: any suspect case should be reported as a matter of urgency to national authorities and to WHO. References: ARITA, I. & GROMYKO, A. Surveillance of orthopoxvirus infections and associated research in the period after smallpox eradication. Bulletin of the World Health Organization, 60: 367-375 (1982); Memorandum on the control of outbreaks of smallpox, London, HMSO, 1975.1

1 See also Management of suspected cases of smallpox in the post-eradication period. Unpublished WHO document, WHO/SE/80.157, Rev. 1.


See Rat-bite fever.

Sporotrichosis (ICD 117.1)

Skin lesion usually on a finger, begins as a nodule then becomes an ulcer, and a series of nodules and ulcers appears on lymphatics draining the area. Complications: rarely arthritis, pneumonitis. Caused by a fungus: Sporothrix schenkii. Laboratory: culture of agent from lesions. Incubation: 1 week to 3 months. Transmission: pricks by thorns of infected plants, or inhalation of spores (pulmonary form); no person-to-person transmission. Occurrence: worldwide; occupational disease of farmers, gardeners, miners; may cause clusters of cases. Control: local or general fungicidal drugs (amphotericin B).

Spotted fever group (ICD 082.9)

Fever, black spot at the site of a tick bite, maculopapular rash on 3rd-5th day, sometimes petechiae. Differential diagnosis: typhus fever due to Rickettsia tsutsugamushi. Caused by rickettsiae. Laboratory: specific serological tests. Incubation: 3-14 days. Transmitted by ticks from animal to man; no person-to-person transmission. Occurrence: Rocky Mountain spotted fever in the Americas (due to Rickettsia rickettsii) (fatality rate 20% if not treated), boutonneuse fever in Africa, India, and the Mediterranean basin (due to Rickettsia conori), Queensland tick typhus in Australia (due to Rickettsia australis), and Siberian tick typhus in the USSR (due to Rickettsia sibirica). Control: antibiotics, repellents, protective clothing in field. Vaccine against Rocky Mountain spotted fever for persons at special risk.


See Rat-bite fever.

Streptococcal pharyngitis (ICD 034.0)

Fever, sore throat with redness, oedema and exudate of pharynx and tonsillar pillars, petechiae, cervical adenopathy, leukocytosis, sometimes only sore throat without exudate. Complications: peritonsillar abscess, otitis media, rheumatic heart disease, glomerulonephritis. Fatality rate: zero. Caused by Streptococcus pyogenes, group A. Laboratory: isolation of agent on special media and determination of group and type; serological tests. Incubation: 1-3 days. Transmission: droplets, articles freshly soiled with pharyngeal discharges. Occurrence: common in 3-12-year age group in temperate climates; inapparent infections more common in warm climates; food-borne outbreaks with high attack rate have occurred on rare occasions caused by food-handlers carrying the bacteria either in the throat or on wounds on their hands. Control: secretion precautions.

Swimmers’ itch (ICD 120.3)

Usually not febrile, dermatitis reaches maximum intensity in 2-3 days and heals in a week or so. Caused by intracutaneous penetration of free-swimming cercariae of bird or mammalian schistosomes which do not mature in man. May occur in many parts of the world. Reference: Weekly epidemiological record, 58: 9 (1983).

Swimming-pool-associated dermatitis (ICD 686.0)

Sharp outbreaks of dermatitis associated with the use of swimming-pools and whirlpools and caused by bacteria such as Pseudomonas aeruginosa have been described. Patients had a maculopapular, vesicular or pustular rash.

Tetanus (ICD 037)

Painful muscular contractions beginning with masseter and neck muscles, extending to the trunk, back muscles; generalized tonic spasticity, intermittent convulsions, spasms, asphyxia, moderate fever. Fatality rate: 35-70%. Caused by the toxin of Clostridium tetani, a bacterium. Laboratory: isolation of the agent usually unsuccessful; no detectable antibody response. Incubation: 4-21 days, usually 10. Transmission: trivial or insignificant wounds contaminated by spores in soil or dust (horse and other animal excreta), possibly by horse and cattle bites, parenteral infections in drug addicts, umbilical contamination at birth, no person-to-person transmission. Occurrence: worldwide, sporadic or small outbreaks. Control: supportive and sedative treatment, antitoxin to neutralize unfixed toxin; immunization at time of wound, or booster dose if already immunized.

Toxic shock syndrome due to Staphylococcus aureus (ICD 785.5)

Sudden onset, high fever, vomiting, profuse watery diarrhoea, myalgia, a macular “sunburn-like” rash. Complication: shock within 48 hours, case-fatality rate 13%. Caused by toxin-producing Staphylococcus aureus associated with the use of vaginal tampons. No person-to-person transmission. Control: secretion precautions.

Toxoplasmosis (ICD 130)

Infection very common but seldom symptomatic. Mild lymphatic form resembles gammaherpesviral mononucleosis (irregular low-grade fever, malaise, cervical and axillary lymphadenopathy). A fulminating, disseminated infection may occur in immunocompromised persons. Complications: congenital toxoplasmosis transmitted transplacentally by mothers infected shortly before or during pregnancy and resulting either in abortion or congenital malformations (mainly of the central nervous system), or no symptoms. Prognosis: usually benign if not complicated. Caused by Toxoplasma gondii, an intracellular protozoan parasite. Differential diagnosis: other causes of lymphadenopathy. Laboratory: Sabin-Feldman test, indirect fluorescent test (confirmation requires paired sera with ascending titres, or single serum with high titre). Incubation: about 5-23 days. Transmission: direct contact with cats (cleaning litter-pans containing infective oocysts); indirect: drinking water contaminated with cat faeces, eating undercooked meat of contaminated domestic animals. Control: treatment with pyrimethamine and sulfadiazine; protection against transmission from infected cats, e.g., prevention of contamination by stray cats of sand where children play; correct cooking of meat.

Traveller’s diarrhoea (ICD 009.1)

Diarrhoea, with or without fever, abdominal cramps, fatigue. Mainly caused by enterotoxigenic Escherichia coli, occasionally by other enteric bacteria, such as Shigella, Salmonella, and Campylobacter. Laboratory: stool culture. Incubation: 12-72 hours. Transmission: faecal-oral, person-to-person or common-source, uncooked food, fruit, vegetables, shellfish, ice-cream, water, drinks, food handlers. Occurrence: mainly in tropical areas; sporadic or clusters of cases in travellers. Control: personal hygiene; excreta precautions.

Trench fever (ICD 083.1)

Sudden or slow onset, fever, headache, muscular pains, splenomegaly, short episode (five-day fever) or relapses, sometimes with macular rash, typhoid-like. Usually non-fatal. Caused by a rickettsia, Rochalimaea quintana. Laboratory: culture of agent on special media, serological tests. Incubation period: 7-30 days. Infective period may be prolonged, possible recurrences. Transmission: faeces of body louse through skin breaks; man and louse are the only reservoirs; louse becomes infective after 5-12 days and remains so for life (5 weeks); no direct person-to-person transmission. Occurrence: worldwide in endemic foci, epidemic under crowded unhygienic conditions. Control: treatment with tetracyclines or chloramphenicol, delousing.

Trichinosis (ICD 124)

Mild or severe febrile disease, sometimes fatal: onset with influenza-like and gastrointestinal symptoms, continuous fever, oedema of eyelids, subconjunctival haemorrhages, muscle pain. Complications: respiratory distress, myocardial failure, hypoproteinaemia, neurological symptoms. Caused by larvae of Trichinella spiralis which migrate from intestine to muscles. Laboratory: a biopsy of skeletal muscle shows T. spiralis larvae (not earlier than 10 days after exposure); adult worms in intestinal mucosa at post mortem examination. Incubation: 1-45 days, usually 10-14 days (shorter in severe cases). Transmission: insufficiently cooked meat, chiefly pork or game: no person-to-person transmission. Occurrence: worldwide, common source, clusters or outbreaks in localized foci. Control: correct cooking of meat.

Trypanosomiasis, African (ICD 086.5)

Fever, intense headache, insomnia, usually a chancre at site of tsetse fly bite, lymph node enlargement (posterior cervical) and occasional rash. Complications: somnolence, central nervous involvement, body wasting, death. Caused by haemoflagellates Trypanosoma brucei gambiense and T. b. rhodesiense. Laboratory: detection of parasite in lymph nodes and blood during the lymphatic phase and in cerebrospinal fluid with elevated protein content during the nervous phase. Incubation: 2-3 weeks (T. b. rhodesiense), up to several months (T. b. gambiense). Occurrence: Africa between 15° N and 20° S latitude in localized foci. Transmission: tsetse fly bite. Control: Prophylaxis with pentamidine for exposed personnel; community measures: reduction of fly population. References: WHO Technical Report Series, No. 635, 1979 (The African trypanosomiases: report of a joint WHO Expert Committee and FAO Expert Consultation); A UNDP/WORLD BANK/WHO CONSULTATION. Control of sleeping sickness due to Trypanosoma brucei gambiense. Bulletin of the World Health Organization, 60: 821-825 (1982); WHO Technical Report Series (The epidemiology and control of African trypanosomiasis: report of a WHO Expert Committee) (in press, 1986).

Trypanosomiasis, American (ICD 086.2)

Many infected persons have no clinical manifestations. Acute disease: variable fever, malaise, lymphadenopathy, hepatosplenomegaly, palpebral oedema, inflammatory lesion at the site of inoculation. Complications (later in life): myocarditis and meningoencephalitis. Caused by Trypanosoma cruzi. Laboratory: demonstration of trypanosome in blood (examination, culture). Incubation: 5-14 days after bite. Transmission: by faeces of infected cone-nosed bugs; blood transfusion. Occurrence: Central and South America. Control: use of bed-nets. Reference: WHO Technical Report Series, No. 202, 1960 (Chagas’ disease: report of a Study Group).

Tuberculosis (ICD 010.9)

Pulmonary tuberculosis (suspected on basis of X-ray examination) may be seen exceptionally as a cluster of recent cases. Caused by Mycobacterium tuberculosis, M. africanum, or M. bovis. Laboratory: tuberculin skin test, examination of smears from sputum, isolation of tubercle bacillus by cultivation. Incubation period: 4-12 weeks. Infective period: may be for years and intermittent. Transmission: by droplets from an infected person, during prolonged exposure; bovine tuberculosis may result from unpasteurized milk or exposure to infected animal. Occurrence: worldwide. Control: antibiotics, search for source and contacts by tuberculin test and X-ray screening; isolation not necessary, disposal of secretion-soiled tissues, disinfection not necessary.

Tularaemia (ICD 021)

Sudden onset, fever, chills, swollen and tender lymph nodes which often suppurate, or typhoidal and pulmonary forms. Fatality rate: untreated, 5%. Caused by a bacterium, Francisella tularensis. Laboratory: cultivation of material from lesions, blood, sputum; serological tests. Incubation: 2-10 days, usually 3. Transmission: contact with blood or tissue of infected wild animals, especially rabbits, hares, and some domestic animals; bites of arthropods (dog ticks, mosquitos), ingestion of insufficiently cooked rabbit or hare meat, contaminated water, inhalation of dust; no person-to-person transmission. Occurrence: North America, Europe, Japan, USSR; sporadic cases or clusters of cases in infected areas during hunting season. Control: streptomycin or tetracyclines, search for source of infection; a live vaccine is of limited use; secretion precautions.

Typhoid fever (ICD 002.0)

Gradual rise of temperature, anorexia, headache, epistaxis, abdominal pain, relative bradycardia, enlargement of spleen and rose spots on the trunk on 7th day (10% of cases). Acute phase: diarrhoea, stupor and delirium. Complications: intestinal haemorrhage or perforation (high fatality rate), pneumonia, abscesses. Fatality rate: untreated 30%, treated 1%. Caused by Salmonella typhi bacilli. Differential diagnosis: paratyphoid fever, salmonellosis, typhus, leptospirosis, malaria, brucellosis, tularaemia, viral hepatitis A, gammaherpesviral mononucleosis, Lassa fever. Laboratory diagnosis: repeated blood and stool cultures; Widal serological test on 7th- and 14th-day sera. Incubation: 7-21 days. Transmission: food (shellfish, vegetables, milk and milk products) or water contaminated by faeces or urine of patients or asymptomatic carriers, food-handlers and flies; exceptionally person-to-person. Occurrence: worldwide, all ages, increased in warm climates; progressive outbreaks. Control: treatment with chloramphenicol, or other antibiotics in case of resistance (laboratory test); supportive treatment may require parenteral nutrition and blood transfusion; isolation (enteric precautions); disinfection (faeces, urine and terminal cleaning); community measures (sanitary disposal of human faeces, chlorination or boiling of water, food hygiene, and fly control); prophylaxis (an oral vaccine may soon be available); notification (optional, obligatory in certain countries). Reference: Salmonella and Shigella surveillance: Guidelines for bacteriological clearance of Salmonella and Shigella excreters. Weekly epidemiological record, 57: 156-158 (1982).

Typhus fever due to Rickettsia prowazekii (ICD 080)

Sudden onset with fever, chills, headache, general pains, prostration. On 5th or 6th day, eruption spreading gradually over the trunk and limbs, except the face, palms and soles, may become petechial and haemorrhagic; pronounced toxaemia. Complication: vascular collapse, gangrene, renal failure, coma; may recur years after as Brill-Zinsser disease. Fatality rate, untreated: 10-40%. Caused by Rickettsia prowazeckii. Differential diagnosis: meningococcaemia. Laboratory: differentiation from typhus fever due to Rickettsia typhi or to Rickettsia tsutsugamushi, by isolation of agent and specific serological tests. Incubation: 12 days (range 1-2 weeks). Transmission: person-to-person by the body louse, infection by rubbing faeces of crushed lice into the bite or inhalation of dust containing infected louse faeces. Occurrence: endemic foci in cold areas, including mountains in tropical areas, in louse-infested populations, outbreaks linked to crowded conditions. Control: treatment with tetracyclines or chloramphenicol and supportive care; application of effective insecticide (resistance may occur) to clothing and bedding of patients and contacts; surveillance of louse-infested contacts for 15 days after insecticide application; effective prophylactic vaccination would require an improved vaccine; notification to WHO (disease under surveillance).

Typhus fever due to Rickettsia tsutsugamushi (ICD 081.2)

Skin ulcers with black scab where infected mite was attached, satellite adenopathy; a few days later, sudden onset of fever, headache, conjunctival injection, generalized lymphadenopathy, followed after 5-8 days by a dull red maculopapular eruption on the trunk, spreading to the extremities, delirium, stupor. Complication: pneumonia, myocarditis. If untreated, fatality rate varies from 1% to 60%, according to rickettsial strain. Caused by Rickettsia tsutsugamushi (ex orientalis). Differential diagnosis: typhus fever due to other rickettsiae, spotted fevers. Laboratory: specific serological diagnosis. Incubation: 10-12 days (range 6-21). Transmission: bite of infected larval trombiculid mites, no person-to-person transmission. Occurrence: localized foci in Central, Eastern and South-East Asia, linked to agricultural activities, hunting, military operations, clusters of cases mainly in non-residents. Control: treatment with tetracylines, supportive care, personal protection against mites (clothes and blankets impregnated with miticidal chemicals, repellents on exposed skin surfaces).

Typhus fever due to Rickettsia typhi (ICD 081.0)

Similar clinically to typhus fever due to Rickettsia prowazekii but milder. Fatality rate 2% Caused by Rickettsia typhi (ex mooseri). Laboratory: differentiation from typhus fever due to other rickettsiae by type-specific serological tests. Incubation: 12 days (range 1-2 weeks). Transmission: by rat fleas which defecate and contaminate the bite site, occasionally by inhalation of desiccated flea faeces. Occurrence: worldwide, clusters of cases in rat-infested dwellings of endemic areas, namely ports. Control: treatment as for typhus fever due to Rickettsia prowazekii, use of rodenticides after application of insecticide powders with residual action to rat runs and burrows. Reference: AL-AWADI, A. R. ET AL. Murine typhus in Kuwait in 1978. Bulletin of the World Health Organization, 60: 283-289 (1982).

Varicella (ICD 052)

For some time during the smallpox post-eradication era, the clinical features of varicella should be carefully differentiated from smallpox, as shown in Table A3.2.

Varicella (chickenpox) is usually benign except in immunocompromised patients, but is more severe in adults than in children. Complications: pneumonia in infants and elderly or immunocompromised adults, encephalitis, streptococcal or staphylococcal infection of the vesicles; zoster (shingles) after a long latent period; congenital malformation in early pregnancy. Caused by varicella-zoster virus (herpesvirus group). Differential diagnosis: smallpox, generalized vaccinia (should disappear with the interruption of vaccination), impetigo, drug rashes. Laboratory: scrapings of floor of vesicles show multinucleated giant cells coloured by Giemsa stain (not in smallpox); vesicle fluid shows round particles by electron-miscroscopy in chickenpox (brick shape in smallpox) and may be used for cultivation of virus (in maximum-containment laboratory in WHO collaborating centre if smallpox is suspected);1 serology is used mainly for epidemiological surveys. Incubation: 13-17 days (range 13-21 days). Transmission: person-to-person, directly very easily by droplets from the nose and throat starting 1-2 days before rash, less easily from vesicles of shingles, indirectly by articles freshly soiled; scabs are not infectious; mild, atypical and inapparent infections are contagious. Occurrence: in winter and early spring in 3-4-year cycles; 75% of the population has had chickenpox by the age of 15 years; outbreaks are progressive in households, schools and other closed communities. Control: no specific treatment (antiviral drugs are under consideration), cleanliness of skin; RESPIRATORY or STRICT ISOLATION until 6 days after onset of rash; disinfection of articles soiled by nose and throat discharges and content of shingle vesicles; immunocompromised contacts should be given specific immune globulin. No international measures, except if smallpox is suspected, in which case telegraphic notification to local authorities and dispatch of vesicle fluid or scabs to WHO (see Annex 5).

1 See Annex 5.

Table A3.2. Clinical features of varicella and smallpox

Clinical feature




Progressive, moderate fever

Sudden, high fever, intense malaise (as in meningitis)


Appears on 2nd day, with continuing fever (in children the rash is often the first sign)

Appears on 3rd-4th day with transient fall of fever for 2-3 days

Begins on the trunk, where it will stay dense, not on palms and soles

Begins on the face and extremities of the limbs including palms and soles, where it will stay dense

Macules become rapidly papular and produce clear vesicles which form crusts without going through the pustular stage

Macules require 4-6 days to transform into papules, vesicles and pustules before producing scabs

Successive crops appear during 4-5 days in the same area, which shows lesions at different stages

Single crop only: all lesions are at the same stage in a given area


Soft, superficial, “teardrop”, not umbilicated

Hard, deep-seated, umbilicated, transform into pustules with rise of fever and prostration


Fall off rapidly leaving temporary granular scabs

Healing is slow and leaves permanent pockmarks



Case-fatality rate, 20-40% (variola major)

Verruga peruana

See Bartonellosis.

Viral hepatitis A (ICD 070.1)

Sudden onset, fever, malaise, anorexia, nausea, abdominal pains followed within 3-10 days by jaundice, dark urine, discoloured stools, altered liver function, elevated serum enzyme tests, asthenia and prolonged convalescence. Complete recovery is the rule (fatality rate less than 0.1%), except for severe forms leading to hepatic coma. Caused by hepatitis A virus (HAV), now considered to be an enterovirus. Laboratory: serological test for detection of specific IgM. Incubation: 15-50 days, usually 28-30. Transmission: faecal-oral, personal contact, contaminated water and food (dairy products, uncooked meat, vegetables, shellfish), transfusion of infected blood. Carriers with mild or asymptomatic infection are frequent, especially children. Occurrence: worldwide, sporadic or epidemic, high prevalence in warm climates in areas with low standards of sanitation, and in certain institutions; explosive outbreaks after exposure to common source of infection, such as food-handlers or water supply contamination. Control: no specific treatment, excreta and blood precautions; investigation of source and contacts; usual personal and community measures against faecal risk; prophylaxis with standard immune serum globulin for contacts and travellers at risk.

Viral hepatitis B (ICD 070.3)

Insidious onset, with anorexia, fever mild or absent, abdominal pains, nausea, vomiting, sometimes arthralgia, followed by jaundice as for hepatitis A. Complications: chronic active hepatitis, cirrhosis, hepatocellular carcinoma, liver necrosis, fulminating cases, hepatic coma. Fatality rate: 1% (6-12% in post-transfusion cases). Caused by hepatitis B virus (HBV). The delta agent is a defective virus which has often been found associated with hepatitis B virus in fulminant hepatitis outbreaks. Laboratory: detection of surface (HBs), core (HBc), and e (HBe) antigens, or anti-HBc and anti-HBs antibodies; these markers follow different courses during the successive phases of the disease. Diagnosis of superimposed delta agent is made by detection of the antigen in the blood or liver, or demonstration of specific IgM in serum. Incubation: 45-160 days (average 2-3 months). Transmission: parenteral, infected blood of patients and carriers, scarifications, toilet articles, injections with contaminated syringes (drug addicts are particularly at risk), blood transfusion and blood products from infected donors, sexual transmission. Occurrence: worldwide, children and adults in developing countries (carrier rate up to 20%), mainly young adults in developed countries (carrier rate less than 1%); sporadic cases or outbreaks in certain groups (homosexuals, prostitutes) and closed institutions; occupational risk in medical professions. Control: no specific drug, prevention with hepatitis B immune globulin for close contacts; an inactivated vaccine is now available; identification of source of infection among carriers; barrier nursing in specialized wards (renal dialysis); screening for carriers before blood donation; excreta and blood precautions.

Viral hepatitis, non-A, non-B (ICD 070.5)

Epidemiologically, there are two distinct entities: blood-transmitted hepatitis and epidemic hepatitis.

(a) Blood-transmitted hepatitis, non-A, non-B

Resembles viral hepatitis B epidemiologically but is generally less severe. Complications: chronic form in 50% of cases, only 10% of which progress to cirrhosis. Possibly caused by more than one virus, not yet identified. Laboratory: exclusion of hepatitis A and B and other causes of jaundice. Incubation: possibly as for hepatitis B. Transmission: infected blood and direct contact. Occurrence: worldwide, accounts for up to 90% of all cases of post-transfusion hepatitis; may also be transmitted by certain batches of clotting factors VIII and IX concentrates which cannot withstand inactivation of hepatitis B; “sporadic” cases may account for 20% of clinical hepatitis. Control: excreta and blood precautions.

(b) Epidemic hepatitis, non-A, non-B

Epidemiologically resembles hepatitis A but serological evidence of HAV or HBV etiology lacking. May be caused by several viruses not yet identified. Incubation: 30-40 days. Transmission: faecal-oral, and blood transfusion. Occurrence: sporadic cases or explosive outbreaks may be caused by ingestion of contaminated food or water; has occurred on several occasions after flooding of rivers. Control: usual personal and community measures against faecal risk; excreta and blood precautions.

Whooping cough

See Pertussis.

Yaws (ICD 102.9)

Initial papilloma (which may ulcerate) for several weeks or months on the face or extremities, followed by dissemination of secondary papillomas in successive crops with periostitis and hyperkeratoses on the palms and soles. Complications: destructive lesions of skin and bones. Caused by Treponema pertenue, a spirochaete. Laboratory: dark-field examination of exudates, syphilis serological tests. Incubation: 2 weeks-3 months. Infective period: several years, may be intermittent. Transmission: direct contact with exudates, probable role of flies. Occurrence: children in humid tropical forests. Control: treatment with penicillin, mass treatment in active foci.

Yellow fever (jungle or sylvatic: ICD 060.0; urban: 060.1; unspecified: 060.9)

First phase is dengue-like followed by a short remission on the 3rd day and a hepatonephrotoxic phase with haemorrhages, which are more obvious than jaundice. Bleeding from nose and gums, black vomit, blood (black or fresh) in stools, anuria, progressive proteinuria, uraemic coma, hypotension, shock, death within 10 days of onset. Fulminating forms: death in 3 days. Fatality rate: up to 80% in severe cases and about 1% if mild and asymptomatic forms are included. Caused by yellow fever virus, a flavivirus. Laboratory: safety precautions, personnel should have been vaccinated at least 10 days earlier; isolation of virus from blood in early stage of the disease or from necropsy specimens up to 12 days after onset and from vector mosquitos; serological tests for specific IgM in single serum or rising IgG in paired sera. Liver biopsy is contraindicated because of the risk of internal bleeding. Incubation: 3-6 days. Transmission: from monkeys to man by certain forest mosquitos (jungle or sylvatic yellow fever) and from person to person by certain domestic mosquitos, mainly Aedes aegypti (urban yellow fever). Occurrence: all age groups in tropical zones of Africa and Americas (Fig. A3.2 and A3.3). Control: bed-nets to avoid contact of patients with mosquitos; individual protection from mosquitos; insecticide spraying during epidemics and breeding source reduction. The live attenuated vaccine requires 7 days to give protection and must be kept in the cold (4-8°C). Urgent notification to authorities and WHO (disease subject to the International Health Regulations). References: WHO Technical Report Series, No. 479, 1971 (Yellow fever: third report of the WHO Expert Committee on Yellow Fever); Prevention and control of yellow fever in Africa. Geneva, World Health Organization, 1986.

Fig. A3.2. Yellow-fever endemic zone in Africa

WHO 85087

Fig. A3.3. Yellow-fever endemic zone in the Americas

WHO 851024

Yersiniosis (ICD 027.8)

Watery diarrhoea in young children (blood streaks in 5% of cases), fever, leukocytosis, enterocolitis and lymphadenitis; mimics appendicitis in older children, low-grade fever. Complication: erythema nodosum, arthritis in adults. Caused by Yersinia enterocolitica and Y. pseudotuberculosis. Laboratory: blood cultures in generalized infections, isolation from stool cultures after refrigeration of specimens. Incubation: 3-76 days. Transmission: faecal-oral; asymptomatic carriers. Occurrence: worldwide; sporadic, food- and water-borne outbreaks, person-to-person transmission, outbreaks in schools, contact with household pets. Control: antibiotic treatment; enteric precautions; investigation of common source. Reference: WHO SCIENTIFIC WORKING GROUP. Enteric infections due to Campylobacter, Yersinia, Salmonella and Shigella. Bulletin of the World Health Organization, 58: 519-537 (1980).