Very few Western travelers ever get seriously ill from cholera, according to thirdworldtraveler.com
The website explains that for a person to become ill large amounts of bacteria from heavily contaminated water would have to be consumed. It explains that the risk of infection in travelers is very low, especially for travelers who follow the usual tourist itineraries and stay in standard accommodation. It adds that cholera is reported in only 1 of 500,000 returning US travelers. The illness in healthy tourists is usually very mild because they rarely ingest the heavily polluted water needed to trigger the disease.
www.thirdworldtraveler.com/Disease/cholera.html
The cholera bacteria may be present in contaminated food, water or shellfish. Shellfish contain cholera for the same reason that they contain hepatitis A virus: because both cholera and hepatitis A virus are found in water, and because shellfish filter hundreds of quarts of water each day in their search for food, shellfish actually catch and concentrate cholera and hepatitis A virus.
Travelers are generally at no risk of cholera if they stay “on the beaten track”, use standard tourist accommodations, eat only cooked shellfish and cooked food, and drink bottled water.
www.chop.edu/service/vaccine-education-center/a-look-at-each-vaccine/cholera-vaccine.html