Cholera carrier studies in Calcutta, 1968. Joint ICMR-GWB-WHO Cholera Study Group, Calcutta, Inia.

Cholera carrier studies in Calcutta during 1966-67 established the prevalence of carriers even in the absence of any overt disease. The carriers excreted V. cholerae intermittently and usually only for short periods. Some, however, excreted intermittently over a long period and thus continued to be potential sources of infection. Intensive field and laboratory studies were carried out during 1968 to determine the incidence of cholera infection in households, in which a case of cholera occurred. An investigation of 492 persons in 23 households, exposed to cholera infection, showed that 96 (20%) persons in 19 households excreted vibrios. Within the first 10 days of the investigation, 86 carriers were detected and another 10 were detected during the next 14 days. Repeated isolations were obtained from 43 (45%) of the 96 carriers at intervals of 1-79 days.One case of overt cholera was linked with a carrier.Of the 96 carriers, 36 (21% of 171 persons) were members of families in which index cases had occurred, and 60 (19% of 321 persons) belonged to other members of the household. Of 103 families examined 54 (52%) were found to be infected.Of 23 index cases 8 (35%) were found to be V. cholerae positive some time after discharge from hospital where they had received rehydration and antibiotic treatment.