Cholera (cont.)

Everyone who drinks or eats food that has not been treated to eliminate V. cholerae (liquids need to be chemically treated, boiled, or pasteurized, and foods need to be cleaned and cooked), especially in areas of the world where cholera is present, is at risk for cholera. The CDC says in regard to cholera risk as of November 2010, "There has been an ongoing global pandemic in Asia, Africa (recently in Zimbabwe in 2008-2009), and Latin America for the last four decades."

Outbreaks occur when there are disasters or other reasons for a loss of sanitary human waste disposal and the lack of safe fluids and foods for people to ingest. Haiti, a country that had not seen a cholera outbreak in over 50 years, had such circumstances develop in 2010 after a massive earthquake destroyed sanitary facilities and water and food treatment facilities for many Haitians. V. cholerae bacteria eventually contaminated primary water sources, resulting in over 530,000 people diagnosed with cholera that resulted in over 7,000 deaths. This cholera outbreak spread to Haiti's neighbor, the Dominican Republic. The Vibrio cholerae strain was closely related to a strain found in Nepal and leads some individuals to blame Nepalese troops that helped with the earthquake disaster as the source of the Haiti cholera outbreak.

There is some evidence that V. cholerae can survive in saltwater and have been isolated from shellfish; eating raw oysters is considered a risk factor for cholera, especially in underdeveloped countries and occasionally even in developed countries. A few people are diagnosed with cholera every year in the U.S. Most of the individuals diagnosed are travelers who were exposed to cholera outside the country, but occasionally, isolated cases are traced to contaminated seafood, usually from states that border the Gulf of Mexico.

It takes about 100 million bacteria to infect a healthy adult. Because of this high number, significant contamination of food or water is required to transmit the disease, and person-to-person transmission is thought to be uncommon.

Some individuals are at higher risk to become infected than others. People who are malnourished or immune-compromised are more likely to get the disease. Children ages 2-4 seem more susceptible than older children, according to some investigators. In addition, researchers have noted that patients with blood type O are twice more likely to develop cholera than others. The reason for this blood type susceptibility is not completely understood. People with achlorhydria (reduced acid secretion in the stomach) and people taking medicines to reduce stomach acid (H2 blockers and others) are also more likely to develop cholera because stomach acid kills many types of bacteria, including V. cholerae.

Source: MedicineNet.com
http://www.medicinenet.com/cholera/article.htm