Changing epidemiology of cholera due toVibrio choleraeO1 and O139 Bengal in Dhaka, Bangladesh

Abstract

SUMMARYAt the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) Dhaka we studied the trends in cholera for the period January 1992 to May 1995.Vibrio choleraeO139 Bengal emerged as a second aetiologic agent of cholera in Dhaka in January 1993. In 1993, the majority of cholera cases was due toV. choleraeO139, withV. choleraeO1 accounting for a small proportion of cases. During the latter part of the study period (Jan 1994–May 1995),V. choleraeO1 re-emerged as the predominant cholera strain. The predominant age group affected in endemic cholera due toV. choleraeO1 was children 2–9 years old, and the organism was isolated from more females than from males at all ages. In contrast, cholera due toV. choleraeO139 caused disease mostly in adults 15 years and older, which indicated that this organism was new in this population. As withV. choleraeO1,V. choleraeO139 was isolated from more females than males. The initial rapid emergence and predominance ofV. choleraeO139 was considered possibly to herald the start of the eighth pandemic of cholera. However, just after a year, the prevalence ofV. choleraeO139 decreased dramatically withV. choleraeO1 resuming the role of the dominant cholera strain. The factor(s) contributing to the dramatic decline in prevalence ofV. choleraeO139 is not well understood.