Cholera is an epidemic disease caused by the bacterium Vibrio cholerae which (depending on the virulence of the infecting strain) causes mild to severe diarrhea, leg and stomach cramps, nausea, and vomiting. The worst cases result in severe dehydration from fluid and electrolyte loss that can lead to shock, kidney failure, and death.
The illness can come on suddenly, and the incubation period can range from 6 hours to a little less than a week. People with depressed immune systems and reduced stomach acidity are at the highest risk of contracting cholera after exposure.
The bacteria cause disease by attaching to the wall of the small intestine and pumping out a polypeptide toxin that causes the aforementioned symptoms.
It is spread by food and water contaminated with the bacteria, usually from feces from individuals who have the disease. Poor sanitation (e.g., untreated water, cooks not washing their hands) is the main cause of cholera outbreaks. However, eating raw or undercooked shellfish that have been taken from sewage-contaminated water can also cause an outbreak. Scientists have found that some strains of cholera are naturally growing in the temperate Gulf Coast waters of the U.S.
Most of the 200-odd cholera cases reported in the United States from 1973 to 1991 are thought to have been caused by people eating underdone shellfish (thus, if you're in Louisiana, you might want to pass on the raw oysters). There have been no cases in the U.S. since then, and there have been no cholera epidemics in the U.S. since 1911. However, the disease can easily develop in any disaster situation where fresh water and washing facilities are not available. Epidemics are common in underdeveloped countries; the disease is the cause of much additional misery in crowded refugee camps around the world.
If you're in an area known for cholera outbreaks, the best way to avoid the disease is to wash your hands religiously and to avoid eating any raw foods, including salads and fruit. Drink only bottled beverages. As the Centers for Disease Control states: "Boil it, cook it, peel it, or forget it." Taking small daily doses of Pepto Bismol may also help ward off the disease, because the bismuth in the medicine acts as an antibacterial agent. However, it also contains salicylate and should not be consumed by people who are allergic to aspirin, who are already taking medicines containing salicylates or who are taking blood thinners. There is also an oral cholera vaccine for people like Peace Corps volunteers who regularly work in cholera-stricken areas.
People with cholera are primarilly treated for dehydration. They are given fluids containing the electrolytes sodium chloride, sodium bicarbonate, potassium chloride, and glucose; these fluids may be given orally (if they are not suffering from vomiting) or intravenously. Tetracycline and other antibiotics are sometimes given; these drugs will shorten the course of the disease, but cholera generally runs its course and the patient will recover on his or her own if the dehydration is taken care of.
References:
http://biotech.icmb.utexas.edu/
http://vm.cfsan.fda.gov/~MOW/chap7.html
http://www.cha.ab.ca/travellers/disinfo_food.html
http://www.disasterrelief.org/Disasters/971112cholera/