Epidemiology of cholera in Delhi--1992.

Cholera is endemic in Delhi and is a highly seasonal disease. Suspected cholera cases are referred to Infectious Diseases Hospital, Delhi. Rectal swabs from 2783 cases were bacteriologically examined during 1992, out of which 1075 were found to be positive for Vibrio cholerae O1 biotype El Tor. First isolation was made on 3 April and the last on 14 December. About 87 per cent isolations were made between May and September, which are summer and monsoon months in Delhi. Detailed epidemiological information was collected for about 198 cases of diarrhoea out of which 103 were confirmed cases of cholera. Half of these cases occurred in children below 10 years of age. The other major group affected was adult females, especially housewives. All the cholera cases occurred in those who were illiterate or educated up to primary level. Important risk factors were: contact with person having similar illness, storage of water in wide-mouthed containers, use of glass or mug to draw water from containers, absence of sanitary latrines and habit of washing hands with water alone after defecation, before cooking and eating food. About 30 percent cases had access to piped water supply which was found safe in Delhi during 1992. The findings suggest that the hygienic practices were more important than contaminated water sources for transmission of cholera in Delhi during the year 1992.