Editorial
C o m m u n i c a b l e D i s e a s e E p i d e m i o l o g y F o l l o w i n g D i s a s t e r s
Michael J Toole, MD
Communicable Disease Epidemiology Following Disasters
See related article, p 362.
The article "Infectious Diseases Following M a j o r Disasters"
by A g h a b a b i a n and Teuscher in this issue o f A n n a l s u n d e r - scores one of the i m p o r t a n t lessons l e a r n e d from studies of p a s t disasters: t h a t much m o r b i d i t y and m o r t a l i t y occurs b e y o n d the initial disaster event and is caused mainly b y communicable diseases. This observation should be a critical factor in the development of a d e q u a t e disaster p r e p a r e d n e s s plans d u r i n g the 1990s, which have been designated by the World Health Organization as the Decade of Disaster Mitigation. Nevertheless, caution should be exercised in gen- eralizing about the role of communicable diseases in the impact of disasters on h u m a n health and survival. The p r o - p o r t i o n of total resources allocated to communicable disease control d u r i n g a disaster relief o p e r a t i o n should be deter- mined as much by the t y p e of disaster as b y its geographic location and the local epidemiology of communicable diseases.
A critical point m a d e b y A g h a b a b i a n and Teuscher is t h a t epidemics of p a r t i c u l a r communicable diseases will only occur after a disaster if the relevant pathogens are endemic to the disaster-affected area. Several a u t h o r s , such as Shears ~ a n d Blake, 2 have noted t h a t epidemics of infectious diseases are relatively uncommon after r a p i d - o n s e t , n a t u r a l disasters such as e a r t h q u a k e s and h u r r i c a n e s . In those acute disasters in which infectious diseases have c o n t r i b u t e d to high death rates, there has been a general increase in the incidence of existing endemic conditions r a t h e r t h a n explo- sive o u t b r e a k s of more exotic diseases such as cholera, typhoid fever, and typhus. Acute n a t u r a l disasters p e r se do not cause an increase in infectious disease incidence; r a t h e r , the s e c o n d a r y effects of the initial disaster event may p r o - mote the increased transmission of endemic diseases and facilitate the establishment of new epidemics. The most i m p o r t a n t of these s e c o n d a r y effects are p o p u l a t i o n displace- ment and destruction of safe water supplies and sanitation facilities. Disruption of existing health services, including hospitals, dispensaries, immunization p r o g r a m s , and vector control activities, also may contribute to increased disease incidence and to higher case:fatality ratios. •
APRIL 1992 21:4 ANNALS OF EMER6ENCY MEDtOINE 4 1 8 / £ 7
EDITORIAL
In contrast, experience has shown that slow-onset disasters such as drought, famine, war, and forced migration have often led to unusually high mortality rates due to communi- cable diseases. The key risk factors for high mortality in these situations appear to have been population
displacement and problems of food access. On one hand, acute population displacement has resulted in large, crowd- ed camps with inadequate clean water and sanitation, condi- tions that favor the rapid spread of enterically transmitted diseases. On the other hand, insufficient access to food has led to high prevalence rates of protein-energy malnutrition among vulnerable groups, such as young children, and con- sequently to increased susceptibility to infectious illness and to elevated case:fatality ratios. Independent of geographic location, measles, diarrheal diseases, malaria, and acute res- piratory infections have consistently been shown to be major causes of childhood mortality in camps for refugees and dis- placed populations in developing countries. These are the same diseases that are the most important causes of deaths in children during nondisaster times.
Although the threat of acute communicable disease epidemics may have been exaggerated in populations affect- ed by rapid-onset disasters, such epidemics have occurred on many occasions in refugee and displaced populations.
Measles epidemics have been common and have caused many deaths in refugee camps in Bangladesh (1978), Somalia (1980), Sudan (1985), and Malawi (1988). 3 In addition, cholera outbreaks have occurred in famine-affected and displaced populations in Thailand (1979); Somalia (1984);
Ethiopia, Mali, and Sudan (1985); Malawi (1988-90); and Turkey (1991).a, s Meningitis outbreaks occurred among refugees in Thailand (1979) and displaced southern Sudanese in Khartoum (1988). 6 Recently, major epidemics of hepatitis E have occurred in refugee camps in Somalia (1986), 7 Ethiopia (1989), and Kenya (1991) (Centers for Disease Control, unpublished data). In certain forced migra- tions associated with war and civil strife, large populations have been relocated into areas where they have been
exposed for the first time to endemic diseases such as schisto- somiasis, trypanosomiasis, onchocerciasis, malaria, and leishmaniasis. Epidemics resulting from such exposures have been a particular problem in populations displaced by the civil wars in southern Sudan and Ethiopia during the past decade.
What are the key applications of this now considerable body of knowledge on communicable disease epidemiology associated with disasters? First, preparedness plans and relief assistance programs must differentiate between the major categories of disasters. Acute, natural disasters cause high death and injury rates at the time of the initial disaster event; prevention and mitigation efforts should be aimed at safer building construction, early warning and evacuation procedures, community education, first aid training, rapid assessment, triage, injury management, and the prompt rehabilitation of damaged water supplies, sanitation systems, and local health services.
In contrast, slow-onset disasters may cause high mortality due to malnutrition and communicable diseases. Prevention of increased communicable disease transmission can be best
achieved by avoiding large-scale population displacement into crowded and unsanitary shelters and camps. In addi- tion, the compounding effects of malnutrition on communi- cable disease incidence and severity must be recognized, and nutrition programs should be mounted promptly when indi- cated.
The effectiveness of relief measures can be monitored by implementing a simple, flexible, and timely health informa- t~onsystem; such a system should include surveillance for communicable diseases of public health importance. Disease surveillance will be most effective if it is adapted from an existing national health information system that has devel- oped practical, field-tested case definitions; identified stan- dard procedures for laboratory confirmation of index cases;
outlined outbreak investigation methods; and trained health workers in their implementation. Disaster preparedness plans should include detailed lists of specific medical supplies that might be needed to control potentially impor- tant communicable diseases. Nonspecific requests for medicines sent to local and foreign donors and relief agencies may have the undesirable effect of attracting large shipments of inappropriate, expired, and poorly packaged drugs and equipment. During the response to an acute disaster, atten- tion should be given to the prevention and appropriate case management of the most common and potentially most lethal diseases. Measles immunization and oral rehydration should be given highest priority. While improvements in water sup- ply and sanitation are crucial for the prevention of transmis- sion of diarrheal diseases, adequate rehydration with oral rehydration salts and continued feeding will significantly lower the case:fatality ratio in patients who do acquire diar- rhea. When epidemics occur, the following sequence should be set in motion: prompt investigation, confirmation of diag- nosis, identification of mode of transmission, active case- finding and treatment, and control activities.
In general, mass immunization of the population has not been an effective epidemic control measure following disas- ters, with the important exception of measles immunization.
One lingering misconception is that mass vaccination plays a role in cholera control efforts. Currently available cholera vaccines have low efficacy, and the World Health Organi- zation does not recommend their use during epidemics. 8 Likewise, mass vaccination has a limited role in typhoid fever control; currently, the most affordable vaccine for developing countries (pareuteral heat-phenol-inactivated vaccine) has relatively low efficacy, requires two serial doses, and has severe side effects. The newly licensed oral live- attenuated vaccine (Ty21) has higher efficacy; however, it is expensive and requires that four serial doses be adminis- tered. 9 Mass immunization with polyvalent meningocoecal vaccine may be an effective control measure in refugee camps situated in areas where a Group A or C meningococ- cal meningitis outbreak has been confirmed.6 However, the relative benefits of mass immunization campaigns must be weighed against the considerable organizational and person- nel commitment required to achieve high coverage of the population.
Similarly, mass chemoprophylaxis of populations in response to outbreaks of cholera, meningitis, and malaria •
9 8 / 4 1 9 ANNALS 0F EMERGENCYME01CINE 2 1 : 4 APRIL1992
EDITORIAL
has not p r o v e n to be a cost- or labor-effective control mea- sure. In certain instances, however, prophylaxis with a p p r o - priate antibiotics should be considered for immediate house- hold contacts of known cases of cholera or meningitis. In the case of m a l a r i a , regular p r o p h y l a x i s with antimalarials may be indicated for such high-risk groups as p r e g n a n t women and infants. Disaster p r e p a r e d n e s s plans and relief programs must place p a r t i c u l a r emphasis on the development of s t a n d a r d case management protocols for common infectious diseases. Treatment guidelines will enable the elaboration of an essential drugs list, r a t i o n a l planning and p r o c u r e m e n t of medical supplies, a n d s t a n d a r d i z e d training of health workers. The epidemiology of disasters, a science largely developed by Michel Lechat in Belgium and John Seaman in the United Kingdom, has now evolved sufficiently to enable relief p r o g r a m s to a p p r o p r i a t e l y target the real needs of disaster-affected populations. As Shears pointed out in a recent review, extensive disaster epidemiology resources now exist in several public health institutes, including the Center for Research on the Epidemiology of Disasters, Louvain, Belgium; the Disaster Health Unit of the Liverpool School of Tropical Medicine, United Kingdom;
Epicentre, P a r i s , F r a n c e ; the Asian Disaster P r e p a r e d n e s s Center, Bangkok, T h a i l a n d ; the P a n American Health Organization, Washington, DC; I n t e r t e c t , Dallas, Texas; and the Centers for Disease Control, Atlanta, Georgia. 1
Myths about disasters a b o u n d , and one of the most com- mon is that epidemics of communicable diseases are
inevitable following disasters. E d u c a t i o n on the real needs of disaster victims should be aimed now at the public health community, governments of r i s k - p r o n e countries, donor and relief agencies, p r i v a t e v o l u n t a r y organizations, and the media. Immediately after a disaster, the media's role is often critical in influencing the n a t u r e of the i n t e r n a t i o n a l commu- nity's response. In A p r i l 1991, for example, the media focused on the possibility of cholera epidemics in the Kurdish refugee camps on the T u r k e y - I r a q b o r d e r , while generally ignoring the very serious p r o b l e m of noncholera, diarrheal illness t h a t eventually caused high mortality.
The imperative of the 1990s is to p u t into practice the lessons learned from the past and to significantly reduce pre- ventable m o r t a l i t y in the n a t u r a l and m a n - m a d e disasters that will inevitably continue to occur. A p p r o p r i a t e surveil- lance and communicable disease control programs will help achieve this goal. []
Michael J Tool& MD
International Healtfi Program Office Centers for Disease Control Atlanta, Georgia
1. Shears P: Epidemiology and infection in famine and disasters. Epidemiol Infect1991;
107:241-251.
2. Blake P: In the Pubfic Health Consequences of Disasters. Atlanta, Centers for Disease Control, 1989, p 7-12.
3. Toole M J, Steketee RW, Waldman R J, et al: Measles prevention and control in emer- gency settings. Bull World Health Organ 1989;67:381-388.
4. Toole M J, Waldman R J: Prevention of excess mortality in refugee and displaced populations in developing countries. JAMA 1990;263:296-302.
5. Centers for Disease Control: Public health consequences of acute displacement of Iraqi citizens: March-May 1991. MMWR 1991;40:443-446.
6. Moore PS, Toole M J, Nieburg P, et ah Surveillance and control of meningococca[
meningitis epidemics in refugee populations. Bull World Health Organ 1990;68:587-596.
7. Centers for Disease Control: Enterically transmitted, non-A, non-B hepatitis--East Africa. MMWR 1987; 36:241-244.
8. World Health Organization: Guidelines for cholera control. WHO/CDD/SER/80.4 Rev 2 (1990). Geneva, Switzerland, WHO.
9. Centers for Disease Control: Typhoid immunization. Recommendations of the Immunization Practices Advisory Committee (AClP). MMWR 1990;39(RR-10):1-5.
APRIL1992 21:4 ANNALS 0F EMERGENCY MEDICINE 4 2 0 / 9 9
