Unusual occurrence of cholera in Delhi during January 1994: epidemiological investigations.

Hundreds of laboratory-confirmed cholera cases occur every year in Delhi. However from 1965 through 1993, no cases of cholera nor carriers of Vibrio cholerae have been detected in the months January and February of all these years. Nevertheless, two cases occurred in January 1994. Both were children who acquired their infection locally. Six hundred fifty-eight rectal swabs collected from possible contacts were negative for V. cholerae. The next isolations could be made only in April, which is the usual beginning of the cholera season. The study suggests that cholera transmission can occur during the winter months in Delhi, but that it is not sustained.