Emergence of a new epidemic strain of Vibrio cholerae in Bangladesh. An epidemiological study.

For decades, epidemic cholera in Bangladesh has produced contrasting pictures of appearance and disappearance of Vibrio cholerae, which until recently, remained confined to the biotypes and to serotypes of V. cholerae O1. The classical biotype continued to survive and coexisted with El Tor biotype in southern Bangladesh despite its disappearance from the rest of the world during the present pandemic. For the first time in history, during the cholera epidemic in 1993, both biotypes (classical and El Tor) of V. cholerae O1 have disappeared and have been replaced by a new strain of V. cholerae non-O1 (designated as O139 Bengal). Environmental changes occurring in the Bay of Bengal may have resulted in the emergence of the new epidemic strain of V. cholerae in Bangladesh.