Cholera is an infection of the small intestine caused by toxigenic strains of Vibrio cholerae, mostly belonging to the O1 serogroup but also to the O139 serogroup. Seven cholera pandemics have occurred since 1817, with six pandemics originating in India and the seventh pandemic originating in Indonesia in 1961. The last outbreak is dominated by an O1 variant named El Tor and has continued to the present. The O139 serogroup was first observed in 1992 in India and associated with epidemics in localized areas.
