Cholera is an infectious disease caused by a bacterium that affects the absorption of water in the small intestine. In severe cases it produces violent diarrhoea within only a few days. The dangerous aspect of cholera is the vast loss of fluid that can occur in a short space of time. It is particularly dangerous in children in developing countries. If untreated, the loss of fluid can be fatal within 24 hours of developing the disease. On the other hand, treatment is simple: replace the fluid with the right mix of sugar and salts - water alone is not adequately absorbed. However, bad cases do require admission to hospital where fluids can be administered straight into the bloodstream via a drip.

Cholera is not really a tropical disease, but is related to standards of hygiene and the quality of drinking water. It was a single well in London in the 1850-60s that was the source of several separate cholera epidemics. John Snow is regarded as a father of public health by his simple but brilliant removal of the handle to the Broad Street water pump!

Improved sanitation and hygiene are still the basic foundation of the fight against cholera in those countries where it occurs.

The incubation period, from infection until the disease breaks out, is generally less than two days, although it can be as long as five days. The infection is often a mild illness with ordinary diarrhoea, and it can even evolve without any symptoms at all. But the individual is still able to pass on the disease.

Typically, cholera begins over quite a short period of time with stomach pains without feeling sick. There may also be a mild fever. Then vomiting and diarrhoea begins, and may continue for several hours.

This is followed by very copious, watery diarrhoea, which is pale and flaky and looks like rice water. The fluid loss may be as high as 1 litre every hour.