Seasonal Cholera from Multiple Small Outbreaks, Rural Bangladesh

Clinical and environmental Vibrio cholerae organisms collected from February 2004 through April 2005 were systematically isolated from 2 rural Bangladeshi locales. Their genetic relatedness was evaluated at 5 loci that contained a variable number of tandem repeats (VNTR). The observed minimal overlap in VNTR patterns between the 2 communities was consistent with sequential, small outbreaks from local sources

Critical Factors Influencing the Occurrence of Vibrio cholerae in the Environment of Bangladesh

The occurrence of outbreaks of cholera in Africa in 1970 and in Latin America in 1991, mainly in coastal communities, and the appearance of the new serotype Vibrio cholerae O139 in India and subsequently in Bangladesh have stimulated efforts to understand environmental factors influencing the growth and geographic distribution of epidemic Vibrio cholerae serotypes. Because of the severity of recent epidemics, cholera is now being considered by some infectious disease investigators as a “reemerging” disease, prompting new work on the ecology of vibrios. Epidemiological and ecological surveillance for cholera has been under way in four rural, geographically separated locations in Bangladesh for the past 4 years, during which both clinical and environmental samples were collected at biweekly intervals. The clinical epidemiology portion of the research has been published (Sack et al., J. Infect. Dis. 187:96-101, 2003). The results of environmental sampling and analysis of the environmental and clinical data have revealed significant correlations of water temperature, water depth, rainfall, conductivity, and copepod counts with the occurrence of cholera toxin-producing bacteria (presumably V. cholerae). The lag periods between increases or decreases in units of factors, such as temperature and salinity, and occurrence of cholera correlate with biological parameters, e.g., plankton population blooms. The new information on the ecology of V. cholerae is proving useful in developing environmental models for the prediction of cholera epidemics

Genetic Variation of Vibrio cholerae during Outbreaks, Bangladesh, 2010–2011

Cholera remains a major public health problem. To compare the relative contribution of strains from the environment with strains isolated from patients during outbreaks, we performed multilocus variable tandem repeat analyses on samples collected during the 2010 and 2011 outbreak seasons in 2 geographically distinct areas of Bangladesh. A total of 222 environmental and clinical isolates of V. cholerae O1 were systematically collected from Chhatak and Mathbaria. In Chhatak, 75 of 79 isolates were from the same clonal complex, in which extensive differentiation was found in a temporally consistent pattern of successive mutations at single loci. A total of 59 isolates were collected from 6 persons; most isolates from 1 person differed by sequential single-locus mutations. In Mathbaria, 60 of 84 isolates represented 2 separate clonal complexes. The small number of genetic lineages in isolates from patients, compared with those from the environment, is consistent with accelerated transmission of some strains among humans during an outbreak

A 4-year study of the epidemiology of Vibrio cholerae in four rural areas of Bangladesh

How Vibrio cholerae spreads around the world and what determines its seasonal peaks in endemic areas are not known. These features of cholera have been hypothesized to be primarily the result of environmental factors associated with aquatic habitats that can now be identified. Since 1997, fortnightly surveillance in 4 widely separated geographic locations in Bangladesh has been performed to identify patients with cholera and to collect environmental data. A total of 5670 patients (53% <5 years of age) have been studied; 14.3% had cholera (10.4% due to V. cholerae O1 El Tor, 3.8% due to O139). Both serogroups were found in all locations; outbreaks were seasonal and often occurred simultaneously. Water-use patterns showed that bathing and washing clothes in tube-well water was significantly protective in two of the sites. These data will be correlated with environmental factors, to develop a model for prediction of cholera outbreaks