Cholera is caused by the bacteria Vibrio cholerae. Bacteria aren’t like you or I, they have a different cellular make-up. The differences between the prokaryotes and the eukaryotes are explained here.
The disease caused by the the Vibrio bacterium kills 120,000 people each year. It causes victims to lose large amounts of water from their body through watery diarrhoea which quickly leads to dehydration and death.
There are very good descriptions of cholera here and here.
To combat the effect of the cholera toxin people need to do more than just drink lots of water. Oral rehydration therapies have been developed to get the water and salts back into the body.
John Snow was the first person to prove that Cholera was a water borne infection and not an airborne disease in a famous experiment carried out at the Broad Street Pump in 1854. After his discovery cholera outbreaks could be contained much more quickly. In the UK his discovery led to massive engineering projects delivering clean water to the masses and providing an effective sewage treatment system. This just goes to show how important epidemiology, the study of the cause of disease, is.
http://www.badscience.net/2008/11/hot-foul-air/