EPIDEMIC CHOLERA IN BURUNDI - PATTERNS OF TRANSMISSION IN THE GREAT RIFT-VALLEY LAKE REGION

Background After a 14-year hiatus, epidemic cholera swept through Buru ndi between January and May, 1992, The pattern of transmission was sim ilar to that in 1978, when the seventh pandemic first reached this reg ion, Communities affected were limited to those near Lake Tanganyika a nd the Rusizi River, The river connects Lake Tanganyika with Lake Kivu to the north in Zaire and Rwanda. Methods To identify sources of infe ction and risk factors for illness, an epidemiological study was carri ed out in Rumonge, a lake-shore town where 318 people were admited to hospital with cholera between April 9 and May 31, 1992, The investigat ion included a case-control study of 56 case-patients and 112 matched controls. Findings Attack rates according to street increased with the street's proximity to Lake Tanganyika (chi(2) test for linear trend, p < 0.01) which suggests that exposure to the lake was a risk factor f or illness, Comparison of the 56 case-patients with matched controls s howed that bathing in the lake (odds ratio 1.6, attributable risk perc entage 37%) and drinking its water (2.78, 14%) were independently and significantly (p < 0.05) linked with illness, No food-borne risk facto rs were identified, Vibrio cholera 01 was isolated from Lake Tanganyih a during, but not after, the outbreak in Rumonge, Isolates from the la ke and from patients with acute watery diarrhoea had the same serotype , biotype, and antimicrobial susceptibility profiles, The number of ca ses rapidly declined when access to the lake was blocked. Interpretati on This study identifies bathing in contaminated surface water as a ma jor risk factor for cholera in sub-Saharan Africa, and suggests that i mproving the quality of drinking water alone will have only limited im pact on the transmission of the disease in the Great Rift Valley Lake region. The similarity in the patterns of transmission during the 1978 and 1992 epidemics suggests that extensive use of the Great Lakes and connecting rivers for transportation and domestic purposes may be the reason for the explosive cholera outbreaks that occur sporadically in this region.