CHOLERA IN A DEVELOPING MEGACITY - KARACHI, PAKISTAN

Despite rapid urbanization and increasing affluence in Karachi, cases of cholera are frequent. We analysed computerized isolation data from the AKUH Clinical Microbiology Laboratory, Karachi, from 1990-6 to exa mine microbiological, temporal and demographic trends in Vibrio choler ae infections. During this period 888 strains of V. cholerae (566 V. c holerae serogroup O1, and 204 V. cholerae serogroup O139) were isolate d from specimens from 886 patients; 214/464 were adult inpatients, and 250/464 paediatric inpatients, the remaining 422 outpatients. Isolati ons peaked between June and August. Overlapping epidemics occurred in 1993 and 1994 of serogroup O1 (May to August), and serogroup O139 (Aug ust to October). All ages and social and economic strata were affected . Forty-four percent of all isolates were from children under the age of 5 years. The mean age of all patients with serogroup O1 infections was 19.6 years (+/-0.9) compared with 36.7 (+/-1.7) for serogroup O139 infections (P < 0.0001, t test). More than a quarter (27%) of all ser ogroup O1 isolates were from babies under 2 years of age. One patient had a serogroup O1 infection followed by a serogroup O139 infection 1 year later. Another patient was infected with serogroup O1 strains 5 y ears apart. Emergence of resistant strains was observed, but by 1996 s erogroup O139 had disappeared. An aquatic organism, cholera neverthele ss continues to take its toll in this city of 11 million situated in a desert.