Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. It has a short incubation period, from less than one day to five days, and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients. Most persons infected with V. cholerae do not become ill, although the bacterium is present in their faeces for 7-14 days. When illness does occur, more than 90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhoea. Less than 10% of ill persons develop typical cholera with signs of moderate or severe dehydration.
Cholera is spread by contaminated water and food. Sudden large outbreaks are usually caused by a contaminated water supply. Only rarely is cholera transmitted by direct person-to-person contact. In highly endemic areas, it is mainly a disease of young children, although breastfeeding infants are rarely affected. Vibrio cholerae is often found in the aquatic environment and is part of the normal flora of brackish water and estuaries. It is often associated with algal blooms (plankton), which are influenced by the temperature of the water. Human beings are also one of the reservoirs of the pathogenic form of Vibrio cholerae.

The first pandemic of cholera of the modern age broke out in 1817-1823; this was followed by five more: 1839-1851, 1852-1859, 1863-1879, 1881-1896, 1899-1923. The 7th pandemic broke out in Celebes (Indonesia) in 1961, and spread in 1970 to most of the countries of Asia the Middle East and Africa; in 1989 the WHO registered 48.400 cases in 35 countries involved. IN January 1991 the pandemic reached almost simultaneously three different coastal regions of Peru, hundreds of kilometres apart and it spread to (Ecuador, Chile, Colombia, Brazil), involving most of southern and central America, some Pacific Island and the United States; at the end of 1992 in the two Americas 750.000 cases of cholera had been registered with 6.500 deaths. Cases were registered in western Europe and some parts of eastern Europe. At the end of 1992 and the following year an epidemic began in Madras and in other parts of India and Bangladesh. The infection spread to the whole of India and only sporadic cases were registered in Pakistan, Nepal, China, Thailand, Kazakhstan, Afghanistan and Malaysia.
Countries infected (15 September 2000) are: Afghanistan, Angola, Belize, Benin, Bhutan, Bolivia, Brazil, Brunei, Burkina Faso, Burundi, Cambodia, Cameroon, Cape Verde, Chad, Chile, China, Colombia, Comores, Congo, Costa Rica, Ivory Coast, Ecuador, El Salvador, Philippines, Ghana, Djibouti Guatemala, Guinea, Guinea Bissau, Guyana, French Guyana, Honduras, India, Iran, Iraq, Kenya, Laos, Liberia, Madagascar, Malawi, Mali, Mauritania, Mexico, Mongolia, Mozambique, Myanmar, Nepal, Nicaragua, Niger, Nigeria, Panama, Peru, Central African Republic, Democratic Congo, Rwanda, Sao Tome and Principe, Senegal, Sierra Leone, Somalia, Sri Lanka, Suriname, Swaziland, Tanzania, Togo, Uganda, Venezuela, Vietnam, Zambia, Zimbabwe. (23/7/2003 Agenzia Fides)