Cholera is a bacterial disease usually spread through contaminated water. Cholera causes severe diarrhoea and dehydration. Left untreated, cholera can be fatal in a matter of hours, even in previously healthy people. Most people exposed to the cholera bacterium (Vibrio cholerae) don’t become ill and never know they’ve been infected. Yet because they shed cholera bacteria in their stool for seven to fourteen days, they can still infect others through contaminated water. Most symptomatic cases of cholera cause mild or moderate diarrhoea that’s often hard to distinguish from diarrhoea caused by other problems.