Cholera

Cholera is a disease of the intestinal tract caused by the Vibrio cholerae bacterium. These bacteria are typically ingested by drinking water contaminated by improper sanitation or by eating improperly cooked fish, especially shell fish. Symptoms include diarrhea, abdominal cramps, nausea, vomiting, and dehydration. Iti is treated with rehydration and antibiotics, but in severe cases, cholera can lead to death.

• About one million Vibrio cholerae bacteria must be ingested to cause cholera in normally healthy adults, although increased susceptibility may be observed in those with weakened immune systems, individuals with decreased gastric acidity (as from the use of antacids), or those who are malnourished.
• The last major outbreak of cholera in the United States was in 1911.
• 1,099,882 cases and 10,453 deaths were reported in the Western Hemisphere between January 1991 and July 1995.
• On average, one case of cholera is reported in the United States every week.

Vibrio cholerae causes disease by producing a toxin that disables the GTPase function of G proteins which are part of G protein-coupled receptors in intestinal cells. This has the effect that the G proteins are locked in the "on position" binding GTP[?] (normally, the G proteins quickly return to "off" by hydrolizing GTP to GDP). The G proteins then cause adenylate cyclase A[?] to produce large amounts of cyclic AMP which results in the loss of fluid and salts across the lining of the gut.

The point of this is that the resulting diarrhea allows the bacterium to spread to other people under unsanitary conditions.

Carriers of the cystic fibrosis gene are protected from the severe effects of cholera because they don't lose water as fast. This explains the high incidence of cystic fibrosis among populations which were formerly exposed to cholera.

References:

• Cholera facts from the United States FDA website (http://vm.cfsan.fda.gov/~MOW/chap7)