Escalating association of Vibrio cholerae O139 with cholera outbreaks in India.

Between December 1999 and December 2000, teams from the National Institute of Cholera and Enteric Diseases, Calcutta, India, examined eight outbreaks of cholera, which occurred in different parts of the country distant from each other. In two of these outbreaks each, only V. cholerae O1 biotype ElTor or V. cholerae O139 could be isolated, while in the remaining four outbreaks, both O1 and O139 were isolated. The interesting feature is the escalating association of V. cholerae O139 with outbreaks of cholera; two of the most recent outbreaks, one in Calcutta and one in Orissa, were caused exclusively by O139. The O139 strains from the six different outbreaks were genotypically closely related. These trends indicate a shift in the outbreak propensity of V. cholerae O139.