Study Site and Population: The study will be conducted in the Infectious Diseases Hospital, Beliaghata, Kolkata. This hospital admits diarrhoea patients of all ages including cholera. The hospital has 3 diarrhoea wards, one for adult men, one for adult women and one for children. It is the designated hospital for admitting all clinically suspected cholera patients from greater Calcutta. Of the total diarrhoea admissions during 1995 to 2002, a little over 25% were children under five,