Risk Assessment: Tools, Techniques, and Their Applications

20.13 Cholera Example

The Broad Street pump in London, England, in 1854 was the source of a cholera outbreak affecting over 500 individuals (10). Dr. John Snow, after interviewing many family members of those affected, found that those individuals affected had all visited one water pump on Broad Street. He then removed the water pump handle, and the cases of cholera abruptly stopped. Dr. Snow, through his investigation, demonstrated a clear epidemiologic process.

Vibrio cholera is a gram-negative bacteria that causes cholera (6). It continues to cause epidemic outbreaks in India and Bangladesh. The bacterium remains within the lumen of the bowel and releases an endotoxin. This endotoxin stimulates the bowel to lose chloride and bicarbonate, which also stimulates the release of sodium and water resulting in profuse, watery diarrhea and mucous.

Prior to 1992, it was thought that there was only one subtype of cholera that caused the profuse diarrheal illness; however, since that time, a new subtype O139 has emerged in Bengal (11).

In the United States, the risk of a cholera epidemic is low, secondary to the water treatment facilities available with the last major outbreak occurring in 1911 (10). It is also necessary to monitor shellfish as the optimal conditions for the growth of V. cholera are salty coastal waters where clams are found. There have been a handful of isolated cases in the Gulf areas of the United States. The risk of a global pandemic from cholera is relatively low. ...