CHANGING EPIDEMIOLOGY OF CHOLERA DUE TO VIBRIO-CHOLERAE O1 AND O139 BENGAL IN DHAKA, BANGLADESH

At the International Centre for Diarrhoeal Disease Research, Banglades h (ICDDR, B) Dhaka we studied the trends in cholera for the period Jan uary 1992 to May 1995. Vibrio cholerae O139 Bengal emerged as a second aetiologic agent of cholera in Dhaka in January 1993. In 1993, the ma jority of cholera cases was due to V. cholerae O139, with V, cholerae O1 accounting for a small proportion of cases. During the latter part of the study period (Jan 1994-May 1995), V. cholerae O1 re-emerged as the predominant cholera strain. The predominant age group affected in endemic cholera due to V. cholerae O1 was children 2-9 years old, and the organism was isolated from more females than from males at all age s. In contrast, cholera due to V. cholerae O139 caused disease mostly in adults 15 years and older, which indicated that this organism was n ew in this population. As with V. cholerae O1, V. cholerae O139 was is olated from more females than males. The initial rapid emergence and p redominance of V. cholerae O139 was considered possibly to herald the start of the eighth pandemic of cholera. However, just after a year, t he prevalence of V. cholerae O139 decreased dramatically with V. chole rae O1 resuming the role of the dominant cholera strain. The factor(s) contributing to the dramatic decline in prevalence of V. cholerae O13 9 is not well understood.