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close this bookMedicine - Epidemiology (ECHO - NOHA - Network on Humanitarian Assistance) (European Commission Humanitarian Office, 1994, 120 p.)
View the document(introduction...)
close this folderChapter 1: Epidemiology and biostatistics
View the documentSection 1 - Presentation and summarising of data
View the documentSection 2 - Measures of disease frequency and association
View the documentSection 3 - Planning and conducting an investigation
close this folderChapter 2: Health Care Planning
View the document(introduction...)
View the documentSection 1 - Priorities and objectives in the context of planning
View the documentSection 2 - Obstacles to planning
View the documentSection 3 - Different stages of the planning process
View the documentSection 4 - Economic evaluation of health care programmes
close this folderChapter 3: Health and development
View the documentSection 1 - Overview and general aspects
View the documentSection 2 - Operational aspects

Section 1 - Overview and general aspects

A - Disasters and public health - Introduction

Over the last decade, public health has become a serious concern in response to natural disasters. There has been an increasing realization that the effects of natural disasters on the health of populations are amenable to study by epidemiological methods. Death rates can be computed for different types of disaster and attack rates can be calculated for the various types of disorder that occur in survivors, and indices of this sort can be used in planning appropriate measures for rescue and relief. There is also considerable interest at present in prevention, especially in the field of earthquake engineering, and such indices will provide essential tools for evaluating the effectiveness of various structural designs and building regulations in reducing death and injuries. The effectiveness of various types of assistance and the long term effect of aid on the restoration of the pre-disaster situation could be assessed as well, if adequate pre-disaster information were available. This article discusses the various epidemiological indices relevant to disaster situations and their value in planning preventive and rescuemeasures.

Death rates in disasters are highly variable, depending on a number of factors such as the type of disaster, the density and distribution of the population, conditions of the environment, degree of preparedness, and opportunity for warning. While the Yellow River floods in China in 1931 are said to have caused several million deaths, the earthquake in 1964 at Anchorage, Alaska, one of the severest ever recorded, claimedonly 115 victims.

While death rates are of little or no use as an epidemiological indicator for the planning of relief and rescue, they are of considerable interest for evaluating the effectiveness of preventive measures aimed at mitigating the effects of disasters, especially in the case of earthquakes.

The number of deaths per hundred houses destroyed in Turkey, a well-known area of tectonic instability, strongly points to some inadequacy in building techniques, making houses particularly lethal in this part of the world. The geographical distribution of damage and loss of life has not been uniform throughout the country, but has been higher in the east, despite a smaller population at risk in that part of the country. This may be due to the type of building material available, since, as one travels east, adobe (unburnt, sundried brick) is the main material used. In Iran, high death rates are associated with houses that are built of insufficiently reinforced adobe in which large concrete slabs are not properly supported.

High case-fatality rates from earthquakes are thus associated with the building techniques use in rural areas in certain countries. This highlights the need for control measures, such as appropriate building legislation and education, to reduce the number of deaths.

In other types of disaster, such as floods, the number of deaths may depend on early recognition of the impending disaster and on an appropriate warning system which allows the population enough time to leave the area or seek refuge. The timing of the warming is then all - important - whether to be on the safe side and run the risk of giving a false alarm, or to wait for definite signs of a disaster and risk giving the warning too late. The problem is similar to the dilemma of sensitivity versus specificity of methods of case-detection that is well known to epidemiologists and public health specialists involved in preventive medicine. The number of deaths may thus be used to check the adequacy of the criteria adopted for early warning of disasters.

Age-specific mortality rates after a disaster may also provide interesting insights into the reaction of the people at the time of impact. In Guatemala, following the 1976 earthquake, age-specific mortality rates showed a bimodal profile.In the town of Patzicia (377 deaths) death rates above the overall rate of 3.5 % occurred among the 5-9 years age group (5.6 %) and among persons aged 60 years and over (5.5 %).

A similar profile was obtained in the town of Sumpango (244 deaths). In both towns, the observed mortality was lower among infants and children 1-4 years old than in the 5-9 years age group, suggesting that parents took special care of their younger and more defenceless children. Following the Bangladesh cyclone in 1970, age-specific mortality also showed a bimodal, but different, distribution : 29 % and 20 % respectively, in the very young (O-4 years) and over 60 years age groups. Data of this kind may thus identify disaster-vulnerable groups, and suggest ways in which appropriate education in communities exposed to natural disasters could reduce the number of deaths.

Effects on the prevalence and incidence of communicable diseases form another important aspect of disaster epidemiology. There may be increased transmission of diseases following the collapse of control systems (for example, interruption of insecticide spraying) and this aspect requires the implementation of a disaster-adapted epidemiological surveillance system with appropriate indices and trends. The consequences of the disruption of routine health services in disaster situations as regards mortality and morbidity are often overlooked. Such effects are more relevant in urban areas and in developed countries. Recently, there have been cases where mortality from ischaemic heart disease, renal failure, and possibly from obstetric causes, have apparently been affected by the unavailability of normal health services. Mental health is another recently identified and perhaps underestimated problem related to disasters, especially in urban areas. Studies are under way to assess the long-term impact on mental health of the Nicaragua earthquake. However, indices of mental health are hard to design, because of the large variety of cultural patterns found in the disaster-struck community and our ignorance about what should indeed beconsidered an adjusted reaction to disasters in exposed individuals.

Another major disaster-related problem is nutrition. It has been widely studied over the last 10 years, following the political uprising in Bangladesh, the civil war in Nigeria, and the droughts in countries south of the Sahara and in Ethiopia. Methods of nutritional assessment have been developed but the indirect effects of famine on the community extend much beyond the epidemiological field. The nutritional indices developed so far, such as weight-for-height, consider only one facet of the problem. Malnutrition, and its corollary food aid, affect the population through a variety of mechanisms, which may range from effects on fertility and abortion, to price and market structures, and the distribution of wealth. Much more study is needed to develop appropriate measurements of the effects of malnutrition and to evaluate the appropriateness of various forms of food aid.

B - Disaster Preparedness: Overview of issues

Introduction

Natural disasters which occur relatively frequently and have a significant impact may be classified into four main categories: floods, earthquakes, cyclones and droughts. Other catastrophic events, such as landslides, avalanches, snow and fires occur less often and threaten smaller proportions of the populated world. The destructive agents in four main classes mentioned above are wind, water (a lack or excess thereof) and tectonic forces. While all these generally cause structural damage, their mortality and morbidity effects are variable.

The disaster cycle can be differentiated into five main phases, extending from one disaster to the next. The phases are : the warning phase indicating the possible occurrence of a catastrophe and the threat period during which the disaster is impending; the impact phase when the disaster strikes; the emergency phase when rescue, treatment and salvage activities commence; the rehabilitation phase when essential services are provided on a temporary basis; the reconstruction phase when a permanent return to normalcy is achieved.

The disaster-induced mortality and morbidity differ between these phasesand are also a function of the prevailing health and socio-economic conditions of the affected community. As a result of this, global statistics on disasters seem to indicate a significantly higher frequency of natural disasters in the Third World than the industrialized countries. Assuming nature not to be conscious of economic differences, a disaster may be defined by the vulnerability of the population to a natural event and not by the mere fact of its occurrence (de Ville de Goyet and Lechat 1976).

Special characteristics of disasters

It is useful to start by locating the four main disaster types on relative scales of lethality, predictability, onset time and impact scope. This ranking provides some guidance towards understanding the variation in mortality impact noted among disaster events across time and space. Figure 1 displays the four scales with the relative positions of the disaster types.

Although drought-related famine is a very special class of disaster, it nevertheless falls within the general paradigm which characterizes natural disasters. Famines are disasters of high predictability. With the exception of the Great Bengal Famine of 1941-43, almost all important famines since then, and certainly the ones of Sahelian Africa and Ethiopia, were more or less foreseen. Famines, in fact, provide an excellent illustration of the fact that the knowledge of impending disaster does not imply that a community can or will take responsive action.

At the other end of the scale, earthquakes tend to be least predictable disasters, striking with little warning. Japan is one of the few high risk countries that have an effective warning and evacuation system, as well as excellent community education programmes (Nakano et al 1974). The earthquake of Niigata (16th June 1964) registered 7.7 on the Richter scale. Although 20,000 houses were destroyed, only 13 people were killed and 315 injured. Due to the quality of its preparedness programmes, Japan suffers very limited mortality despite the high number of seismic shocks it registers (Akimoto 1972).

In terms of lethality, earthquakes present the greatest risk of death to those affected (Table 1). Onset delay is also the shortest in earthquakes, which is related, to a certain extent, to its low predictability. Famine, on the other hand, has a slow build up period before it reaches acute emergency proportions. Floods can be somewhat ambiguous in their onset characteristics. They can be slow-developing and fairly predictable such as the annual floods in the plains of the Ganges in India or in the Itajai River basin in Brazil, but nevertheless regularly cause a number of deaths and a certain amount of damage (Civil Defense of Santa Catarina, personal communication, 1983). Acute and catastrophic floods are usually generated by cyclones or tidal waves; examples are the ones in Philippines (1984) and Bangladesh (1985). Floods cause somewhat lower mortality than other disasters, but the scope of damage is generally wider and more pervasive.

Trends and differentials in disaster related mortality

On a global level, the mortality generated by natural disasters showssome interesting tendencies, creating the beginnings of an analytical framework within which specific impacts may be systematically analysed for robust indicators, efficient needs assessment or preparedness and rehabilitation planning. The mortality form disasters is a function of risk, development and coping or adjustment capacity (preparedness). Table 2 displays comparative data on these from a number of countries.

The official disaster data reveal two important variations in disaster mortality : a temporal increase and a geographical correlation.

Time trends in disaster mortality

Mortality per event - Between the two ten-year periods, 1960-69 and 1970-79, a significant increase in average mortality per event is noted in all categories except perhaps in floods where direct mortality is generally low (Table 3).

The greatest increase is noted in earthquakes, which takes a quantum leap from one period to the next. The mortality in 1960-69 was 750 deaths per earthquake whereas in the following ten-year period the death toll per event went up to 4 871 deaths per earthquake.(It is interesting to note here that the total number of earthquakes requiring international assistance did not increase significantly from one period to the next). The huge increase in earthquake mortality is partially explained by the Tangshan strike of 1976 in China which contributed more than half of the entire ten-year period death toll. The official estimate of 224 000 dead accounts for exactly 47 per cent of the total number dead due to earthquakes during this time. But even allowing for the Tangshan quake, the death mortality per strike remains as high as 1,780 per earthquake compared to 750 in the previous decade. Population density (Lechat 1984), structural quality (Glass et al 1977), time of strike (De Bruycker et al 1983) and intensity of seismic activity (Alexander 1985) seem to be the main risk factors, but they fail to explain adequately the high mortality in earthquakes.

Local conditions, evidently, play a bigger role than expected in determining disaster mortality.

Mortality per 1 000 exposed - The mortality rates per 1,000 exposed to disasters increase significantly over the two decades for all types of disaster except floods, although the increase is relatively slight in earthquakes. This stability in the mortality rates of earthquakes is mainly due to its being a high risk disaster with comparatively localized effects. The greatest increase is observed in drought-related famines where the population get progressively weaker from previous famines and succumb in each successive crisis in greater numbers. Floods show a slight improvement, as it were. However, the mortality impact of floods may be hypothesized as being typically spread over the period following the flood rather than being a direct and immediate effect of the event. This increase in the mortality rate possibly reflects the inability of current disaster management policies to reduce the vulnerability of a community. Despite significant disaster assistance, and aid of nearly one billion dollars in the 1970-78 period, the increase in mortality, controlling for the number of events, indicates a steady decline in the resistance of the populations to disasters (Stephens et al 1982).

Regional differentials in disaster mortality

Geographically, the mortality generated by disasters is consistently and positively correlated to the level of the economy. Table 4 presents some figures of mortality classified into three national income categories.

Mortality rates, controlling for the number of disaster events, are substantially higher in poor countries than in the richer ones. The classification is, of course, gross and the data demand closer analyses for better definition of risk factors and vulnerability patterns amongst the severely affected populations. Such analyses can have direct impact on programme planning and policy-orientation. Table 4, however, does serve to indicate the important influence of the prevailing socio-economic conditions on the eventual disaster impact (Cuny 1983, Shah 1985). For predictive and needs assessment purposes then, the prevalent socio-economic and health conditions prevalent in the affected community could be a better determinant of the epidemiological impact than the physical characteristics of the event.

As seen in Table 4, disaster-generated mortality increases dramatically as economies descend the income scale. Barring a deliberate selectivity of nature in her allocation of high intensity disasters to low income countries, a less "natural" explanation is the differential power of communities to resist and recuperate from shock. Table 5 presents some data on the 1971-72 earthquakes of Managua(Nicaragua) and San Fernando Valley (USA) (Seaman 1984).

The comparison reveals some interesting points. Speaking "naturally" of the two earthquakes, the seismic activity level of the California earthquake was significantly higher, registering 6.6 on the Richter scale compared to 5.6 in Managua. (One unit increase is an important proportion due to the logarithmic scale of Richter readings). On the Mercalli scale (measuring the extent of physical damage over surface area) the California quake caused major damage (IX-XI level damage) over 100 km2, whereas Managua registered a lower level of damage to a smaller area of land. The population directly affected by the earthquake in California was 13 times that of the earthquake in Managua. Despite all physical conditions indicating to the contrary, the mortality in Managua was somewhere around 5,000 deaths compared to 60 deaths in California. Similarly, in 1974, Hurricane Fifi left an estimated 8,000 dead in Honduras, crashing through at a windspeed of about 250 km/h and causing80 per cent disruption of impact area. In the same year, Cyclone Tracy killed 49 in Darwin, Australia, with a similar windspeed and proportion of impact zone disruption. The selectivity of impact can also be observed on a more localized scale. The Guatemala earthquake in 1976killed about 1,200 people and left 90,000 without homes in the cityalone, but almost exclusively from the slum populations. Shanty towns and slum areas in the burgeoning metropolises of several high risk Third World countries are especially fragile in all kinds of disasters. The unprecedented increase in these slum populations has contributed to the inflation of the disaster victims in the recent years. The Jakarta shanty towns, for example, where floods frequently cause the canals-cum-latrines to overflow into the living quarters of the slum-dwellers, have created epidemics of typhoid and skin and gastro-intestinal diseases and raised infant and child mortality. Flooding in low-lying areas of Bangladesh has exacerbated endemic cholera and other diarrhoeal diseases.

Disaster related morbidity

The data on morbidity (namely injuries and disease) after a disaster are remarkable by their absence or incomparability. The definition of injury, when registered, is largely unstated and reporting of diseases largely incomplete. This has resulted in a series of observations, some anecdotal, some systematic, but nearly all fragmentary. There is clearly an urgent need for standardized reporting of injuries and cause of death (preferably using a standard format such as the International Classification of Disease). Without such standardization, disaster planning and management remains an ad hoc activity and analyses of thekind attempted here can only be undertaken somewhat superficially.

Injury profiles of natural disasters

There are some recorded figures available on injuries sustained in earthquakes where authorities registered and published morbidity data. It is uncertain what qualified as injury and, more importantly, the bias introduced by those who were not treated in hospital. There are even fewer data on non-traumatic morbidity. Classification bias and general incomparability pose important problems for those making analyses for programme or policy purposes.

In the case of earthquakes, the disaster type most prone to causing traumatic injury, fractures constitute the major portion of the impact. Fractures of the extremities are significantly more frequent than any other sort. In the Tashkent (1966) and Ashkabad (1948) earthquakes, two of the few instances where injuries were classified according to type, about 69 per cent were fractures of the limbs (Beinin 1981). Fractures of the extremities as a proportion of injuries sustained in Managua (1971) and Iran were 77 per cent and 58 per cent respectively (Whittaker 1974, Saidi 1963). In the recent volcanic eruption of Colombia, gaseous gangrene was the second most serious morbid condition next to suffocation. The Mexico earthquake seemed to have relatively few injuries compared to deaths, although the official figures are not yet available. Most injuries, be they lacerations in cyclones or fractures in earthquakes, tend to occur during the catastrophe itself or in the very immediate post-impact phase.

Clearly, in both earthquakes and cyclones, structural quality of housingis a major determining factor of the extent and type of injury, which is, in effect, a proxy variable for the socio-economic level of the community or the houselhold (Haas et al 1977). The relationship between injury and death and other variables not directly related to the catastrophe is discussed later in the paper.

Disease profiles of natural disasters

Despite popular belief, major epidemics are fairly rare events after natural disasters (de Ville de Goyet and Lechat 1976, Seaman 1984), especially in industrialized countries. Some risk exists in developing countries where sanitation is poor and endemicity of many communicable diseases is normally high. A severe malaria epidemic occurred after Hurricane Flora in Haiti in 1964, ostensibly caused by the multiplication of breeding places for mosquitoes in the damaged areas. However, the interrelationships between the disaster and the hurricane are more complex and epidemiologically interesting than this explanation indicates (Lechat, personal communication, 1985). Overcrowding and breakdown of fragile sanitation systems could, conceivably, provoke epidemics in developing countries. An epidemic ofleptospirosis was reported in Recife, Brazil, after floods in 1975 (Correa et al 1972). These are, generally, fairly unimportant in scope. Of a more serious nature are those brought on by famine conditions, such as the cholera epidemic in Somalia in 1985 and meningitis in Ethiopia earlier. Camp conditions, reduced resistance and breakdown of the social systems are possibly the provoking factors for these epidemics, but to what extent and how these factors are associated with the diseases cannot be conclusively established without specific study. Usually, however, disasters do not generate "new" diseases unless they are brought in by migrating populations, as has been observed in the recent African famines. Floods tend to exacerbate endemic communicable diseases in populations, especially if sanitary and sewage systems are primitive or, as is more often the case, non-existent. A regional variation in diseases similiar to that seen between developed and developing countries is noted within a developing country. The incidence rates during a cholera epidemic in Bangladesh were found to becorrelated to education and income. The poorer sections of the affected region used canal water for drinking and washing purposes and presented, furthermore, a generally lower resistance to infections. The incidencerate of the disease per 1,000 families with no schooling was 16.3whereas it was 8.2 among families with at least one high school graduate (Levine et al 1976). In famines, the synergy between malnutrition and infectious diseases gives it an altogether different dimension as compared to others. Communicable and nutritional deficiency diseases in famine disaster are, in fact, the principal manifestation of the event.

Long-term impact of disasters

The long-term impact of disasters, possibly the most pervasive and destructive phase, expresses itself variously. Disaster-induced death and disability of an earning member of a family implies a lifetime's loss of revenue and possible destitution.

A study by Karakos et al (1983) after the earthquake of 1980 in Thessaloniki, found that 50 per cent of all the families with at least one death lost their only working member and thus experienced a direct decrease in income. In developing countries, where the informal sector is an important source of revenue for a large proportion of the population and social security is less developed, such a loss can be fatal to the surviving members of the family.

In flooding disasters, salt-water contamination of subsistence and marginal land indicates not one, but several, harvests lost. For nutritionally and economically fragile populations, this means a rise in mortality as a secondary effect of the disaster.

Similiarly, death of breeding stock of herdsmen and loss of capital or tools of trade due to water damage, cyclones or earthquakes effectively destroy the means of livelihood of these families (PAHO Disaster Reports 1981). Finally, the death of a mother has a devastating effect on small children, raising the morbidity rates among them (Patil and Koshy 1984). A great deal of empirical work, clearly, needs to be done in order to evaluateaccurately the complete health impact of a disaster. So far, impact evaluation stops at counting the dead.

Policy implications for the health sector

The increasing interest shown in the impact of natural disasters by researchers in disciplines other than engineering, geology and meteorology has had a salutary effect of raising questions on current international and national disaster policy and relief action. The growing body of literature emphasizing the importance of discriminating between the geophysical event and its human consequences is provoking organizations and governments to take another look at disaster relief. This is an encouraging turn of events given the large calamities witnessed in the last three years and the worrisome increase in the number of victims, dead or destitute (Wijkman and Timberlake 1984, OFDA 1982.

Futhermore, with non-emergency developmental aid and co-operation between the first and third worlds grinding to a slow halt, the substantial resources generated by public appeals for disaster assistance demands an efficient and cost-effective use, oriented towards a long-term resolution of the problem instead of an emergency, stop-gap measure.

It is not difficult, even with the patchy and incomplete data available, to demonstrate that the physical characteristics of a natural event do not satisfactorily explain its impact. This paper has cited several comparative instances illustrating this point. Most natural disasters and the damage associated with them are characteristic rather than accidental features of the afflicted community (Hewitt 1983). Although this is well proven (but not widely accepted) in the case of famines, it is less well documented in the more acute disasters. Two of the largest famines since World War II have been in countries with a normal or more than normal food production during the famine year. Rivers (quoted in Wijkman and Timberlake 1984) observed that Ethiopia was a net exporter of food in 1973, and both Bangladesh and Bengal produced more grain in 1974 and 1941 respectively than in the preceding years (Wijkman andTimberlake 1984, Sen 1983). Drought sometimes serves as a trigger mechanism for a famine, but the disaster remains a largely poverty-related catastrophe with a very weak causal relationship to food supply. Similarly, the impact of other disasters is a function of the physical and economic resistance of the population.

This distinction between the event and the impact brings into a so far simple situation a host of messy, complex and difficult socio-political and economic considerations. The essence of the vulnerability issuelies in the fact that the communities can "cope with earthquakes but not with their fellows" (Brecht 1965). Japan, as cited earlier, has minimized earthquake-generated damage despite frequent shocks of high magnitude, where Nicaragua and Guatemala are unable to withstand quakes of much lower intensity.

Disaster relief has traditionally been based on policy formulated from charitable motives drawing on critical and emergency care approaches. This has made it a primarily medical activity, involving surgical units flown out with specialist teams and field hospitals equipped with sophisticated life-saving apparatus. On the other hand, research and development in natural catastrophes has concentrated almost exclusively on climate monitoring, radar tracking, flood barriers and other middle to high technology devices. Finally, the charitable nature of disaster relief permits policy to bedictated by the principle that any aid is good aid, thereby generating anecdotes in the literature on the superfluous, inappropriate and frequently, absurd relief packages.

Lechat (1981) has pointed out that the even volunteers, who tend to descend upon the scene, can be a serious liability in a crisis situation, due to their inexperience andredundancy.

As far as policy is concerned, two observations are in order before discussing further the implications. First, although medical care (in so far as surgical and critical care is implied) appears largely unnecessary, health and public health, having played thus far a small but significant role, have a responsibility and potential in this area. Second, the central issue in management and relief in natural disasters has to be recognized as the reduction of vulnerability to disasters of the community and, within it, the population at risk. The progressive diminution of mortality and morbidity impact of a catastrophe should be the main health policy objective of disaster management.

The extraction of disaster relief from its comfortable niche of charity and emergency care would force planners to address structural issues of the availability, equity and appropriateness of health care in the community. This widening of scope permits and, indeed, demands the inclusion of health planning for disasters in the on-going health plans of the region, thus providing an existing working base and infrastructure. A disaster response could be successfully incorporated into the training of the health workers and their activities. The fundamental tenets of primary health care may be applied to disaster preparedness and prevention programmes, in so far as both involve community participation, multi-sectoral objectives, the use of local resources and building human resource capability.

These aspects of primary health care are especially relevant in disaster management for the several reasons. External emergency disaster assistance is rarely, if ever, either on time or particularly appropriate. This is not due to any sluggishness on the part of the distant agencies, but rather the result of inadequacies in communication, assessment of need, accessibility and other difficulties. It has been observed that families, friends and neighbours search, evacuate and extricate their own in the immediate aftermath of a disaster and that by the time external relief teams are functional on site, a very large majority of the total dead have already died (DeBruycker 1983). In other words, those that die do so within the very first hours of the event, and immediate emergency rescue and care are provided by the local inhabitants. Those that survive the first twenty four hours generally survive without major bodily harm. In addition, the survivors, contrary to expectations, are rarely in a panic and disorganized. In fact, they act with calm and common sense to manage to the best of their abilities their own affairs (Wijkman and Timberlake 1984). External emergency relief, therefore, is largely expensive, wasteful and not particularly effective.

This, however does not imply that disaster relief should be abandoned, because in a catastrophe people need help and the resources exist.

It simply indicates that external disaster relief should focus on reducing population vulnerability and invest in structural changes in health care organization and accessibility of the population. It should also provide training and education at the local level for emergency activities such as evacuation, first aid and so forth. This rationalization of policy would provide the communities with the tools and knowledge by which they could defend themselves against future hazards. Disaster assistance resources could be deployed to expand the primary health care structure and train their personnel in emergency shelter management, rapid epidemiological surveillance and control, food distribution and needs assessment and recording and registration.