Morbidity and Mortality Surveillance in Rwandan Refugees -- Burundi and Zaire, 1994

In April 1994, resumption of a longstanding conflict between the Hutus and Tutsis -- the two major ethnic groups in the central African countries of Burundi and Zaire -- resulted in civil war and mass genocide in Rwanda. An estimated 63,000 (primarily Tutsi) refugees subsequently moved from Rwanda into northern Burundi, and 500,000 refugees fled to Tanzania (Figure_1). In early July 1994, as armed strife subsided, many Tutsis returned home to Rwanda, and an estimated 1 million Rwandan Hutus fled to Zaire, and 170,000 fled to Burundi. To monitor the health status of the refugees, the Office of the United Nations High Commissioner for Refugees (UNHCR) and nongovernmental organizations (NGOs) working in refugee camps in both countries established systems for rapid surveillance of morbidity and mortality. This report presents the findings of these systems during May-September 1994 (the period of the most intensive population migration) and indicates that mortality was high among refugees in camps in both countries. Burundi

In May 1994, morbidity surveillance was initiated by using health-unit data collected by NGOs in seven refugee camps in northern Burundi. Denominator data were derived from UNHCR estimates used to calculate quantities of rations. Clinical case definitions for major causes of morbidity (bloody diarrhea, nonbloody diarrhea, cholera, malaria, acute respiratory infections {ARIs}, measles, meningitis, trauma, and other conditions) had been developed previously by the Ministry of Health in Burundi (1). Mortality data were collected from three sources: a camp grave watcher; home-health visitors who interviewed families of deceased persons; and the camp health unit, which distributed free funeral shrouds to the families of deceased persons.

In May, daily crude mortality rates (CMR) varied substantially among the camps, ranging from zero to eight deaths per 10,000 population per day. By July 1994, the CMR had declined to zero to two deaths per 10,000 per day. The most commonly reported causes of death were diarrheal diseases, and the major causes of morbidity were malaria, bloody diarrhea, and ARI.

An outbreak of nonbloody diarrhea in one camp in Ngozi had a peak incidence of 980 cases per 100,000 per week; Vibrio cholerae O1, biotype El Tor, serotype Ogawa, was isolated from stool samples obtained from a sample of affected persons. Interventions included improvements in the camp water system (e.g., chlorination) and intensive health education and latrine-maintenance efforts; the incidence of new cases declined to 350 cases per 100,000 per week within 5 weeks.

During May, the approximately 26,000 persons living in camps in Ngozi and Kayanza were vaccinated against meningococcal meningitis after suspected cases were reported during May 1-14. The average weekly rate (54 cases per 100,000 per week) had substantially exceeded the epidemic threshold rate (greater than or equal to 15 cases per 100,000 per week) (2). Neisseria meningitidis, serotype A, subsequently was isolated from cerebrospinal fluid samples obtained from patients. Zaire

In August 1994, morbidity and mortality surveillance was initiated by using information collected in NGO clinics in the three primary refugee camps in eastern Zaire and the town of Goma. Case definitions for six major causes of morbidity and mortality (bloody diarrhea, nonbloody diarrhea, malaria, measles, meningitis, and ARI) were standardized among all health agencies working in the camps. The numbers of deaths occurring in the camps were obtained from three sources: a body-collection system that recovered bodies along the roadside using trucks, tallies of bodies buried in mass graves, and health agency reports of deaths occurring in camp hospitals. Initially, a range of denominators (600,000-800,000) was used because no accurate records were available of the number of refugees in the camps; however, in September, UNHCR determined the number of refugees to be 600,000. Based on these denominator data, the CMR ranged from 34.1 to 54.5 deaths per 10,000 per day during August 8-21 (using the denominators of 600,000-800,000), then decreased to 2.5 per 10,000 per day on September 29 (using the denominator of 600,000) and to 0.2 per 10,000 per day on November 30 (using the denominator of 600,000).

The highest rates of illness and death were associated with an epidemic of diarrhea first documented at NGO clinics; subsequently, V. cholerae O1, biotype El Tor, serotype Ogawa, was isolated from stool samples obtained from patients. From July 21 (when sentinel surveillance for diarrheal disease was initiated) through August 14, approximately 62,500 cases were reported from camp health centers (rate *: 31.2-41.7 cases per 10,000 per day). Camp surveys and clinic reports suggested that approximately 37,500 (60%) of these cases (watery diarrhea) resulted from infection with V. cholerae. However, by August 4, the incidence of bloody diarrhea exceeded watery diarrhea, and infection with Shigella dysenteriae type 1 was confirmed in persons with bloody diarrhea. During August 8-14, a total of 15,543 cases of bloody diarrhea (rate *: 27.8-37.0 cases per 10,000 per day) were reported. Findings of a survey in one camp indicated that 47% of persons with fatal diarrheal disease had never visited a health-care facility. Comparison of death rates calculated using data from the surveillance system and the numbers of bodies collected suggested that greater than 90% of deaths from all causes occurred outside health-care facilities.

From August 14 through September 11, the daily incidence of ARIs among persons in all of these camps ranged from 5.6 to 7.4 cases per 10,000 persons *. The incidence of malaria could not be calculated because cases were not laboratory confirmed and were included in the category "fevers of unknown origin"; however, the incidence of fevers of unknown origin ranged from 15.8 to 21.0 cases per 10,000 persons *. Although the reported incidence of measles was low (201 cases) during this period, the United Nation's Children's Fund (UNICEF) initiated a measles vaccination campaign aimed at all children aged less than 5 years -- estimated to be 25% of the total population. In addition, because 83 cases of meningococcal meningitis type A were confirmed during August 1-16 and exceeded World Health Organization (WHO) recommended threshold limits, a vaccination campaign was conducted during late August and early September.

Reported by: United Nations High Commissioner for Refugees, Geneva, Switzerland. Ministry of Health, Zaire. World Health Organization, Bujumbura, Burundi. Div of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion; Div of HIV/AIDS Prevention, National Center for Prevention Svcs; International Health Program Office, CDC.

Editorial Note

Editorial Note: Death rates among refugee populations may be substantially increased when exodus is rapid and large numbers of persons are displaced. During nonemergency situations, the daily CMR in developing countries is 0.5 per 10,000 persons (3). The death rates in Zaire (34-54 deaths per 10,000 per day *) were among the highest to be documented during recent refugee emergencies, while those among refugees in Burundi were similar to those recorded in border camps in Thailand in 1979 (10.6 per 10,000 per day), in Somalia in 1980 (10.1 per 10,000 per day), and in Ethiopia in 1991 (4.7 per 10,000 per day) (3). In Zaire, a high proportion (initially 90%) of deaths occurred outside health-care facilities, indicating either that health-care services were not accessible to a high proportion of severely ill persons or services at clinic sites were exceeded by demands. This finding emphasizes the need for establishing community rehydration programs at the beginning of the emergency phase.

The differences in rates of illness and death among refugees in Burundi and Zaire probably reflected three factors: 1) the daily number of camp arrivals, 2) the total camp size, and 3) the magnitude and speed of spread of the outbreaks of cholera. In particular, in Burundi, 60,000 refugees arrived during the first wave in April and 170,000 arrived during July; in comparison, approximately 1 million refugees arrived in Zaire during a 5-day period. These rapid influxes of large numbers of persons facilitated transmission of infectious diseases and hindered establishment of emergency health-care services in both areas.

The surveillance systems in Burundi and Zaire assisted in the identification of outbreaks, implementation and assessment of interventions (e.g., control of diarrheal diseases through the provision of clean water and sanitation systems, distribution of soap, and training of clinical staff in aggressive rehydration therapy), and recognition of the need for increased health-care services. The experiences in both countries underscore the needs for simplicity and for targeting surveillance efforts during the emergency phase in refugee camps.

References

1. Ries AA, Wells JG, Olivola D, et al. Epidemic Shigella dysenteriae type 1 in Burundi: panresistance and implications for prevention. J Infect Dis 1994;169:1035-41.

2. Moore PS, Toole MJ, Nieburg P, Waldman RJ, Broome CV. Surveillance and control of meningococcal meningitis epidemics in refugee populations. Bull World Health Organ 1990;68:587-96.

3. CDC. Famine-affected refugee and displaced populations: recommendations for public health issues. MMWR 1992;41(no. RR-13).

* Rates were calculated using the denominators 600,000-800,000.

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