Cholera, sometimes known as Asiatic cholera or epidemic cholera, is an infectious gastroenteritis caused by the bacterium Vibrio cholerae. Transmission to humans occurs through the process of ingesting contaminated water or food. The major reservoir for cholera was long assumed to be humans themselves, but considerable evidence exists that aquatic environments can serve as reservoirs of the bacteria.

Vibrio cholerae is a Gram-negative bacterium that produces cholera toxin, an enterotoxin, whose action on the mucosal epithelium lining of the small intestine is responsible for the characteristic massive diarrhoea of the disease. In its most severe forms, cholera is one of the most rapidly fatal illnesses known, and a healthy person may become hypotensive within an hour of the onset of symptoms; infected patients may die within three hours if treatment is not provided. In a common scenario, the disease progresses from the first liquid stool to shock in 4 to 12 hours, with death following in 18 hours to several days without oral rehydration therapy.