Investigation report of an epidemic of typhoid fever.

An explosive common-source epidemic of typhoid fever, probably the world's biggest, occurred in Sangli Town (Maharashtra State), India, between December 1975 and February 1976 when, with the incidence rate of 6.59% over this 12-week period, probably more than 9000 cases occurred in a population of about 135 000. Faecal contamination of municipal water supply, which was receiving unsatisfactory and inadequate chlorine treatment, was responsible for the epidemic. Contamination at suitable intervals resulted in a heavy build-up of S. typhi in the population. Massive central contamination of the ill-maintained municipal water-supply system with faecally-contaminated waste-water from a population of about 37 000, in which there were thought to be over 250 typhoid cases, ultimately resulted in the explosive epidemic. The episode underlines the importance of proper maintenance of water supply and excreta disposal systems.