Vibrio cholerae O139 Bengal: the new serogroup causing cholera

Abstract

The 1990s have witnessed a resurgence in the global incidence of cholera. With the spread of the seventh pandemic of cholera into Latin America, the number of countries reporting cholera cases has dramatically increased from 35 in 1984 to 54 in 1991. More alarming, in recent times, has been the emergence, in late 1992 in south India and the subsequent explosive spread of a new cholera-causing serogroup classified as Vibrio cholerae O139 Bengal. The predominant age-group affected in the O139 epidemics in India and Bangladesh was adult, indicating a new infection in a community with no preexisting immunity. V. cholerae O139 has aroused much international interest and has been proclaimed as the eighth pandemic strain of cholera. Several investigations indicate that the genetic elements constituting the virulence cassette and the genes regulating these virulence genes of the O139 serogroup are similar to those of the O1 E1 Tor biotype. The chemical composition of the O139 lipopolysaccharide, and the presence of an extracellular carbohydrate fraction on the surface, place the O139 serogroup as a distinct entity, probably better equipped to survive than its predecessors. In the span of 2 years since its genesis, V. cholerae O139 Bengal have spread into several countries in the Asian continent, and imported cases of O139 cholera have been reported from many parts of the world. This review traces the origin, spread and our current understanding of V. cholerae O139 Bengal.