Part 4: Epidemics

This chapter of the module will improve your knowledge regarding:

the difference between endemic disease, threatened epidemic diseases and emergency epidemics

the factors which cause outbreaks of communicable disease

the importance of conducting epidemiological studies and surveillance to predict and mitigate epidemics

need for immediate intervention measures to control epidemics

need for follow up studies to determine weaknesses in health care systems in order to prevent future epidemics.

Introduction

Epidemics of infectious diseases such as cholera, meningococcal meningitis, typhoid, typhus and hepatitis pose considerable threat to the populations of developing countries, but also still occur in industrialized nations. An epidemic is defined as the occurrence of a disease, known or suspected to be of infectious or parasitic origin, that is unusually large or unexpected. An epidemic often evolves rapidly into an emergency situation, thus a prompt response is needed. Epidemics may be hazards in themselves, but may also accompany and intensify the misery brought on by other disasters.

The term "epidemic" may be applied to any pronounced rise in incidence and is not restricted to sudden outbreaks. Slow epidemics of leprosy, for example, may spread and develop over generations. New and unrecognized epidemics occasionally arise such as AIDS (acute-immunodeficiency syndrome) which was detected in the United States in 1981 through routine surveillance of pneumonia cases.

EPIDEMIC HAZARD DATA SHEET

Leading causes of death In 1980

Causes	Developed Countries %	Developing Countries %
Infectious and parasitic diseases	8	40
Cancers	19	5
Circulatory diseases	54	19
Perinatal conditions	2	8
Injury/poisoning	6	5
All others	12	23

Source: WHO. 1987

Explanation of terms

A distinction is made between "point-source" and "propagated disease" epidemics. In a point-source epidemic, susceptible individuals are exposed to a source of toxins, as with food poisoning which results in a large number of cases in a short period of time. A propagated disease epidemic arises when organisms are spread in the community by passage from person to person resulting in an initial rise in the number of cases which is less abrupt than in point-source epidemics.

Most developing countries are host to a variety of endemic communicable diseases. The term "endemic" refers to the constant presence of a disease or disease agent within a specified area. These include malaria, typhoid, hepatitis, sleeping sickness and relapsing fever. Where a disease is endemic, a certain number of cases above normal usually must occur for an outbreak to be considered epidemic.

Q. What is the difference between "point source" and "propagated disease" epidemics?

A. ____________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________
______________________________________________________________ ______________________________________________________________ ______________________________________________________________

ANSWER Point source epidemics are spread to humans from a particular toxic or infectious source, and propagated disease epidemics are spread from one person to others, from these to still others, forming a chain of infection.

Point-source

Propagated

Causal phenomena

The number of reported outbreaks of communicable disease has increased in recent years for a number of reasons. National and international travel is increasing daily and takes place over greater distances. Explosive urban development is associated with poor sanitary conditions and crowding. An increase in incidence of sexually transmitted diseases has occurred due to changes in behavior and long term dormant symptoms. Some of the increases, however, may be attributed to better health care coverage in developing countries and more thorough reporting of outbreaks.

Many endemic diseases are capable of becoming epidemic if environmental or host carriers change in a way that favors transmission. Possible examples include:

Exposure of non-immune persons, generally by immigration from a non-endemic area (such as tourists or refugees).

Ecological changes may favor the breeding of an insect vector, such as the mosquito in the rainy season.

Increase in human movements due to markets or favorable seasonal conditions increasing the points and frequency of contact.

Poor sanitation causing contamination of food or water supply.

Decline in nutritional status.

A potential epidemic may be predicted by increase in numbers in the organism in carriers or animals. In plague, a disease carried by fleas on rodents, for instance, an "epizootic" (the parallel term for animals equivalent to an "epidemic" for humans) occurs prior to the epidemic.

Q. What are the reasons cited in the text for the increase in the number of reported outbreaks of communicable disease in recent years?

A. ____________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________
______________________________________________________________ ______________________________________________________________ ______________________________________________________________

ANSWER The increase in the number of reported outbreaks of communicable disease in recent years may be attributable to: 1) increased national and international travel 2) urban development booms causing crowding and poor sanitation 3) changes in social behavior 4) increased health care coverage (which may lessen incidences of outbreaks yet increase medical reporting of all cases)

General characteristics

A "threatened" epidemic can be anticipated when certain circumstances are present, such as: a susceptible population; the presence or impending introduction of the disease agent; the presence of a mechanism for large scale transmission (such as a contaminated water supply or a vector population).

An epidemic "emergency" can only be defined within the larger context in which it occurs, but may include the following characteristics:

1) risk of introduction and spread of the disease in the population

2) expectation of a large number of cases

3) the disease is of such severity as to lead to serious disability or death

4) risk of social and for economic disruption from presence of the disease

5) national authorities are unable to cope adequately with the situation because of a lack or insufficiency of:

- technical or professional personnel
- organizational experience
- necessary supplies or equipment (drugs vaccines, laboratory diagnostic materials, vector control materials, etc.)

6) a danger of international transmission.

Predictability

Epidemiology is the study of the distribution and determinants of disease in humans. These studies assist health workers to predict epidemics to some extent and to initiate prevention and preparedness measures. Epidemiological studies serve to:

Describe the health status of the community. By examining the frequency and distribution of health problems, clues are obtained which promote understanding of disease, leading to interventions for prevention and treatment.

Provide data to plan and evaluate health care. If health care is poor or not available, the possibility of epidemics increases.

Describe the natural history of disease and allow disease classification.

Constraints to predictability occur in newly formed communities such as refugee camps or resettlement villages where medical histories are not known and immunities to local vectors may be lacking.

Constraints to predictability occur in newly formed communities such as refugee camps or resettlement villages where medical histories are not known and immunities to local vectors may be lacking. Further, the environment may be unplanned or unestablished and factors such as source of water supply uncertain. Health care may be transitional or not sufficiently focused on prevention, due to lack of supplies and trained personnel.

Factors contributing to vulnerability

Poverty is the major factor contributing to vulnerability.

Poverty is the major factor contributing to vulnerability. Vulnerable populations also consist of individuals who are not immune to diseases or who are subjected to poor nutrition, poor sanitation, poorly organized health care delivery, drug resistant diseases such as chloroquin resistant malaria and endemic diseases.

Typical adverse effects

Epidemics cause illness and death. Usually the number of cases reported is far lower than the number that actually occur. Secondary effects are social and political disruption and economic loss. Epidemics may worsen already traumatic or life threatening situations such as those found in famine, emergency evacuations and refugee camps.

Specific preparedness measures

For most epidemic disasters, typical patterns of public health may be anticipated and can be planned for well in advance. The challenge for national health programs is to make emergency prepared (...) ongoing health services while strengthening overall (...) following measures can be integrated into long-term ongoing programs and emergency preparedness programs.

Organizational preparedness

Structural components - The delineation of responsibility must be very clear among the organizations involved in emergency response. In many countries, the Ministry of Health holds responsibility for initiating response. Roles of agencies at the governmental (regional and local), nongovernmental and international levels should be clearly defined.

Contingency plans - It is important to identify in advance the epidemics likely to occur and to plan for their mitigation. The components of a contingency plan are

- early warning through epidemiological surveillance

- procedures for performing assessments to determine the nature and existence of an epidemic

- updated lists and maps of health facilities, inventory of NGOs which may assist

- standardized procedures for involvement of all agencies including roles of international organizations

- procedures for obtaining funds and other resources such as transportation, medicines, laboratory analysis, health workers, communications

Training - Train national staff at different levels in emergency preparedness and response for epidemics.

Assessment of an epidemic

When notification of a possible epidemic arrives, an investigation employing a systematic routine or checklist should be followed in spite of possible feelings of panic. Two different approaches are compared below. The questions on the right are part of the "Rapid Health Assessment" method publicized by WHO.

Assessment Checklist

1) Verification of the diagnosis	What is the definition of a case?
2) Confirmation of the existence of an epidemic	How many cases are there?
3) Identification of affected persons and their characteristics - Case histories - Search for additional cases	What is the geographic distribution of cases?
4) Definition and investigation of the population at risk	What is the size of the population at risk?
5) Formulation of a hypothesis as to source and spread of epidemic	How serious is the clinical course of the disease?
6) Management of the epidemic - Treatment of cases - Prevention of spread and initiation of control measures - Writing a report for the record - Continued surveillance of the population	Is the epidemic spreading? Can local health services cope?
7) Experimental verification of agent of disease and mode of spread	What are the modes of transmission?

Q. What are the three major components of institutional preparedness?

A. ____________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________
______________________________________________________________ ______________________________________________________________ ______________________________________________________________

ANSWER The three components of institutional preparedness for epidemic outbreaks are: 1) Structural components of the institutions including clearly set roles and responsibilities. 2) Viable contingency plans for possible outbreaks 3) Training for national staff at all levels.

Control measures for outbreaks

An outbreak of communicable disease may be controlled by:

eliminating or reducing the source of infection;

interrupting transmission;

protecting persons at risk.

If determination of the source of infection is likely to take some time, procedures to interrupt transmission must be initiated immediately. Transmission of disease occurs by person to person transmission (by feces, urine, oral secretions, blood or articles contaminated by those) or a common source (vectors such as insects, rodents, food, water, soil, air) or both. Person to person transmission may be stopped by reducing contact, quarantine of highly contagious persons, and improving sanitation. Vector control requires trained personnel and equipment. Any necessary immunizations and medications should be administered.

With the advance of life threatening epidemics such as AIDS, community participation is particularly vital.

AIDS mural in downtown SPaulo

Sid Kane/UNDP, World Development, June 1990.

Community health education

Learning about health, not just avoidance of poor health but promotion of positive health, can be a lifelong endeavor. Simple preventive health measures may range from hand washing and keeping flies away from the face to complex matters such as preventing sexually transmitted diseases. In developing countries, health education can be incorporated into school curricula and clinic settings to help change harmful cultural or traditional practices. Campaigns to reach adults may take the form of visits by rural health workers or publicity through media such as posters, radio and TV.

Community health education can help stem epidemics by alerting individuals to signs and symptoms of disease and stressing the importance of reporting cases to local health clinics. With the advance of life-threatening epidemics such as AIDS, community participation is particularly vital. The loss of productive individuals or their immobilization by illness inflicts not only personal and economic hardships on families but also on the society as a whole

Q. In designing a community health education program it is important to teach the methods that can be used to stop the spread of communicable disease. List the three basic ways in which an outbreak of communicable disease can be controlled.

A. ____________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________
______________________________________________________________ ______________________________________________________________ ______________________________________________________________

ANSWER Communicable disease can be controlled by: 1) eliminating or reducing the source of the infection 2) interrupting transmission 3) protecting persons at risk

Typical post-disaster needs

International aid may be required when an outbreak develops that cannot be contained with national resources. Advance planning should establish what might be needed in the event of an outbreak. Agencies that may provide assistance include International Committee of the Red Cross (ICRC) and UN agencies such as UNDRO, WHO, UNICEF and UNDP.

Evaluation of control measures

Indicators must be chosen which will assess the success of control measures such as decrease in the daily rate of occurrence and low likelihood of reoccurrence. Cost effectiveness of treatment and cost of preventative measures may be compared and determinations made of the amount of human suffering that was avoided.

Post epidemic analysis should document information in a final report form so that it may be publicized.

CASE STUDY

Yellow fever epidemic in Mali - an endemic disease becomes epidemic

Identifying weaknesses in national epidemiology surveillance

Yellow fever, a mosquito-borne viral infection, continues to be a major threat in endemic zones of Africa where the virus reappears even after long periods of dormancy. Outbreaks have occurred in Africa resulting in thousands of deaths. Available statistics largely underestimate the prevalence of the disease, due to its occurrence in many remote areas where there is a lack of medical services and unfamiliarity of medical personnel with the disease. Serological surveys carried out in all parts of Africa since 1932 have delineated the boundaries in which the disease has occurred.

Mass yellow fever immunization campaigns were initiated in West Africa in 1940 and resultant disappearance of cases led to neglect in administering the immunizations. In 1958, some virus activity occurred in Zaire and later in Sudan. The most severe outbreak occurred in Ethiopia in 1960-62 when a dramatic epidemic affected the southwest region of the country and 3,000 deaths were reported. Realistic estimates are more in the line of 30,000 deaths occurring out of 100,000 cases. Yellow fever had never penetrated this area before, thus no immunity existed and many were affected. Over the past 25 years, several other outbreaks of the disease were recorded.

From September to November, 1987, a yellow fever epidemic broke out in western Mali which precipitated a wide scale immunization program. A total of 305 cases and 145 deaths were officially reported but true numbers were probably about five times higher. The Mali Ministry of Health operates a rapid information system whereby a radio network linkage to district levels report disease information weekly to headquarters. If an unusual health problem is reported, a team is sent to the field to initiate an epidemiological investigation and recommend public health measures.

The disease was reported initially by health workers as hepatitis, a common mistake as jaundice is characteristic of both diseases. Inefficient means were used to secure blood samples for testing and resulted in delays in diagnosis. When blood samples were finally obtained, they had to be Sent to a different country for analysis, further delaying the confirmation of disease. Later examination of records showed that patients at different clinics with the same symptoms received different treatments.

A post-disaster analysis concluded that four deficiencies existed:

Insufficient training - The medical personnel were not fully aware of the history or symptoms of yellow fever and the need to differentiate these from other jaundice producing diseases. They did not process the blood samples correctly and include complete patient information. Beside the lack of training for diagnosis and treatment, the medical personnel were not aware of the correct procedure to follow once the cases were suspected. No active case finding was performed and communication to alert other stations was incomplete. Further, health workers did not demonstrate that they understood the importance of completing standardized forms for reporting.

Lack of equipment for laboratory confirmation - Inadequate local and national facilities caused a delay in diagnosis.

Inadequate action plan for epidemic control - The incident demonstrated the need for more detailed procedures of identifying and confirming the disease, assessing the magnitude and severity and implementing prevention and control.

The low utilization of health services was a very important feature of this case - Only those cases in which people died or went to the health clinic because they were severely ill were reported. This may also explain the lack of vaccine coverage for the victims. Reasons for low utilization may include poor accessibility from remote areas or low confidence in medical care provided. A need exists for surveillance teams to seek out cases by visiting rural sites.

Recommendations to strengthen the epidemiological surveillance capabilities in Mali in view of the limited resources and a high risk population included:

1) Training of local health personnel to carry out case detection rather than wait for a specialized unit to respond perhaps from a long distance.

2) Creation of a fund to mobilize epidemic preparedness activities.

3) Development of regional coordination for surveys, immunizations and vector control, and the provision of technical assistance and pooling of resources.

Q. 1) What other reasons besides presence of jaundice might have led the Mali health workers to initially diagnose hepatitis? 2) From this description, what errors occurred in the procedures that may have caused the disease to become an epidemic?

A. ____________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________
______________________________________________________________ ______________________________________________________________ ______________________________________________________________

ANSWER 1) If they were unaware of the history of yellow fever, they may have believed it to be eradicated. They may also have believed that the patients had been vaccinated. 2) When patients showed sings of a contagious disease, the health workers did not go out to look for more cases to determine the scope of the problem. Emergency and control measures were not initiated until the laboratory report came in, and cases may have multiplied during that time. Different treatments indicates conflicting information in the health care system. Treatments given may not have included the control measures needed.

References

Barker, D.J.P., and A.J. Hall, Practical Epidemiology, Churchill Livingstone, 1991.

Bres, P., Public Health Action in Emergencies, World Health Organization, Geneva, 1986.

CDC Monograph, "The Public Health Consequences of Disasters," 1989, U.S. Department of Health and Human Services, Centers for Disease Control, Atlanta, Georgia, September, 1989.

Kane, Sid, "Brazil Takes Aim on AIDS", in World Development, UNDP, June 1990.

Kurz, Xavier, "The Yellow Fever Epidemic in Western Mali, September-November 1987: Why Did Epidemiological Surveillance Fail?, in Disasters, Vol. 14 No. 1,1990, p. 46-54.

Sandler, R.H. and T.C. Jones, Medical Care of Refugees, Oxford University Press, New York, 1987.

UNDRO, Disaster Prevention and Mitigation, Preparedness Aspects, Vol. 11, United Nations, New York, 1984.

WHO, Emergency Preparedness and Response: Introduction to Rapid Health Assessment Emergency Relief Operations, January, 1990.

WHO, Prevention and Control of Yellow Fever in Africa, Geneva, 1986.