Cholera is an acute diarrhoeal illness caused by a bacterium Vibrio cholerae. It is characterised by painless diarrhoea and vomiting. Most people infected with V. cholerae do not become ill. When illness occurs, 90% develop uncomplicated vomiting and diarrhoea. Fewer than 10% of cases develop the severe form of the disease, which, if not treated can be rapidly life threatening due to dehydration and shock. In severe cases, the diarrhoea can be very watery and profuse and it is this loss of fluid that can make the disease so serious.