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Cholera Epidemic After Increased Civil Conflict --- Monrovia, Liberia, June--September 2003

Since 1989, civil war in Liberia has resulted in the displacement of hundreds of thousands of persons. In June 2003, as rebel forces approached the capital city of Monrovia (2003 estimated population: one million), an estimated 300,000 internally displaced persons (IDPs) settled in private homes with family members, public buildings, and other sites. Because of fighting during June--July, the normal collection of health data by the Liberian Ministry of Health (MoH) was interrupted. In June, cases of cholera were confirmed by international nongovernment organizations. To estimate the magnitude of the outbreak, in August, the World Health Organization (WHO) conducted a retrospective review of data collected by health organizations during June--August 2003 but not reported to MoH. Additional data were collected from an emergency surveillance system that began operation on August 25. This report summarizes the results of that analysis, which indicated that as of September 22, a cholera epidemic was ongoing in Monrovia. During the week ending October 20, a total of 1,252 cases of suspected cholera were reported (WHO, MoH, unpublished data, 2003). As of November 12, the epidemic was contining. The epidemic began in June (Figure) and was associated temporally with increased fighting and the movement of IDPs. Because cholera transmission was probably attributable to an acute shortage of clean water, poor sanitation, and crowded living conditions, international and Liberian organizations attempted to supply IDP settlements with sufficient potable water and began chlorinating wells. To stop cholera transmission and avoid additional illness and death, further preventive measures are needed.

Although the majority of health-care facilities in Monrovia were closed during June--July, by mid-August, local and international organizations and MoH were operating five inpatient hospitals, four cholera-treatment centers, seven oral rehydration clinics, and at least 30 general outpatient clinics. Before August 25, each organization classified cases of diarrheal disease differently, making it difficult to apply a standard surveillance definition. Cases most closely approximating the standard WHO-recommended case definition for use in cholera outbreaks (i.e., acute watery diarrhea in a person aged >5 years) were included in retrospective case counts. After August 25, the majority of facilities that reported data to the emergency surveillance system used a case definition that included acute watery diarrhea in children aged 2--4 years.

During June, the number of persons treated for cholera increased from 49 to 426 per week. During June 2--September 22, of an estimated one million permanent residents and 172,000 IDPs in Monrovia (1), 16,969 (1.4%) persons sought medical care for an illness consistent with the surveillance case definition for cholera. The number of persons treated for cholera increased sharply in early June, and stool cultures confirmed the presence of Vibrio cholerae O1; the case-fatality ratio in cholera-treatment centers was <1%. The number of persons treated per week peaked in mid-July at 935, declined to 387 in the last week in July, and increased again to 2,352 during September 16--22, the last week for which data are available.

V. cholerae O1 was isolated in the laboratory of St. Joseph Catholic Hospital in Monrovia from stool specimens obtained from six patients during June 9--13; no additional serotyping or antimicrobial susceptibility data were available. V. cholerae was isolated again at the same laboratory later in the outbreak from stool specimens obtained on August 26 from five of six adults with suspected cholera who were admitted to cholera-treatment centers at Samuel K. Doe Stadium and John F. Kennedy (JFK) Hospital, the main referral hospital in Monrovia.

Community-based mortality data were unavailable. However, three cholera-treatment centers operated by Médecins sans Frontières (MSF) reported that during June 2--September 15, of 4,746 hospitalized patients with illnesses consistent with a diagnosis of cholera, 37 (0.8%) patients died. During this period, 3,073 (64.8%) hospitalized patients had severe dehydration. Data from the cholera-treatment center operated at JFK Hospital by MSF Belgium were used to compare the outbreak in 2003 with the number of reported cholera cases in previous years. This center, unlike other health facilities that provided services in Monrovia during the 2003 outbreak, has treated cholera patients for the previous 4 years. During June--August, a total of 2,648 cholera patients were treated in this facility, compared with 450--655 patients during comparable periods in the previous 4 years.

Reported by: S Briand, MD, World Health Organization, Geneva, Switzerland. H Khalifa, MD, Médecins sans Frontières; CL Peter, MD, Medical Emergency Relief International (Merlin); OJ Khatib, MD, FK Bolay, MD, World Health Organization, Monrovia, Liberia. BA Woodruff, MD, MA Anderson, MD, Div of Emergency and Environmental Health Svcs, National Center for Environmental Health; ED Mintz, MD, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note:

Although the precise number of cholera cases and cholera deaths is unknown, available data indicate that a large cholera epidemic is occurring in Monrovia. Cholera is endemic in Liberia during the rainy season (March--November), but the number of persons treated during June--August 2003 was substantially higher than the number treated during comparable periods in recent years. Cholera transmission is facilitated by crowded conditions, poor sanitation, and lack of clean water, all of which were exacerbated in Monrovia during June--July by increased fighting and population movement. The supply of clean water in Monrovia is limited, and for the previous 10 years, the piped water distribution system has not functioned in the majority of Monrovia neighborhoods. Availability of water from other sources (e.g., vendors or wells) was disrupted by the fighting, and frequent heavy rains washed contamination into shallow, unprotected wells from which a substantial number of persons obtain water. In addition, the trucking system that provides IDP sites with chlorinated water from deep borehole wells has not supplied sufficient quantities. An assessment on August 22 indicated that in 14 selected IDP sites, the water supply averaged 1.8 liters of clean water per person per day (2), compared with the recommended minimum in emergencies of 15 liters per person per day (3).

The case-fatality ratio in cholera-treatment centers operated by MSF was substantially lower than that observed in other large cholera outbreaks (4). Treatment in these centers, which specialize in the rehydration of cholera patients, probably was adequate. In addition, because cholera is endemic in Monrovia, the population might have had some immunity, leading to less severe or shorter duration of illness.

The surveillance data described in this report likely underestimate the total number of cholera cases and deaths in Monrovia. Reporting of illnesses from health facilities was incomplete, the cholera case definition varied initially by facility, and mortality reporting was lacking. In addition, not all ill patients might have sought treatment. In other major cholera outbreaks in similar emergencies, a substantial proportion of persons ill with cholera did not report to health-care facilities and thus never were recorded by health-care facility--based surveillance (4). The majority of health-care facilities in Monrovia stopped functioning or were inaccessible during the worst periods of fighting, which probably reduced the number of cholera patients seeking treatment. The number of deaths that occurred at health-care facilities not operated by MSF is unknown.

Public health authorities use morbidity and mortality surveillance data to evaluate the effectiveness of curative and preventive interventions in emergency situations. If collection of such data ceases in an emergency, public health surveillance should be reestablished as soon as possible. All public health organizations should agree on which agency is responsible for coordinating surveillance data collection, analysis, and distribution. In addition, health-care facilities should use standard case definitions and report data with the same periodicity.

Although cholera in Monrovia is most likely waterborne, which water sources are primarily responsible for cholera transmission is unknown. Other routes of transmission, including transmission by contaminated food, also might exist. Investigations are needed to identify the specific routes of cholera transmission so that targeted and effective preventive interventions can be implemented. Until such investigations are completed, past experience and empirical data should guide prevention efforts. Chlorination of wells is expensive and has not been proven effective during a cholera epidemic (5). Cholera transmission is more effectively prevented by provision of increased amounts of clean water (6), health education (7), and chlorination of water in protected household containers (8). In previous years, the seasonal increase in the number of cholera cases persisted through December. Until effective control measures are taken, the current epidemic will result in additional cases of illness and death.

References

  1. United Nations Office for the Coordination of Humanitarian Affairs. Liberia humanitarian briefing issue 1. Monrovia, Liberia: United Nations Office for the Coordination of Humanitarian Affairs, August 26, 2003.
  2. United Nations Children's Fund (UNICEF). Preliminary report on a rapid assessment of the water and sanitation situation in greater Monrovia. Monrovia, Liberia: United Nations Children's Fund, August 12--22, 2003.
  3. The Sphere Project. The Sphere Project: Humanitarian Charter and Minimum Standards in Disaster Response. Geneva, Switzerland: Oxfam Publishing, 2000.
  4. Goma Epidemiology Group. Public health impact of Rwandan refugee crisis: what happened in Goma, Zaire, in July, 1994? Lancet 1995; 345:339--44.
  5. Rowe A, Angulo F, Roberts L, Tauxe R. Chlorinating well water with liquid bleach was not an effective water disinfection strategy in Guinea-Bissau. Int J Environ Health Res 1998;8:339--40.
  6. World Health Organization. Guidelines for Cholera Control. Geneva, Switzerland: World Health Organization, 1993.
  7. Quick RE, Thompson BL, Zuniga A, et al. Epidemic cholera in rural El Salvador: risk factors in a region covered by a cholera prevention campaign. Epidemiol Infect 1995;114:249--55.
  8. Reller ME, Mong YJ, Hoekstra RM, Quick RE. Cholera prevention with traditional and novel water treatment methods: an outbreak investigation in Fort-Dauphin, Madagascar. Am J Public Health 2001; 91:1608--10.


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