The germ Vibrio cholerae is excreted by a sufferer in the stools and vomit. It can then be spread directly to other people if they touch the patient and then fail to wash their hands before eating.

The germ can also contaminate food or water supplies. In the latter case this will cause an explosive outbreak because many people will ingest the vibrion in a short space of time. Once inside the intestine, the cholera vibrion multiplies and produces a toxin.

This toxin causes the cells lining the intestine to secrete massive volumes of fluid... leading to the characteristic diarrhoea and vomiting. The diarrhoea is odourless and looks like rice water.

A patient under treatment can lose more than 50 litres of fluid during a bout of cholera. A person who is not treated will die of dehydration well before this. In fact death usually occurs when 10 to 15 per cent of the total body weight is lost. In severe cases this may take only a couple of hours.