Illustration of a cholera outbreak in India. Cholera is a bacterial infection of the small intestine that is transmitted via contaminated food or water. The bacterium causing the disease produces a toxin that causes diarrhoea and severe dehydration. It was often fatal before modern treatments were developed. It spread in infected water supplies and killed millions in the 19th century. The bacterium causing the disease (Vibrio cholerae) was not identified until 1883. Illustration from La Medecine Illustre by Dr Gerard Paris (1888).