Definition of Typhoid fever:

Typhoid fever is an infection that causes diarrhea and a rash -- most commonly due to a type of bacteria called Salmonella typhi (S. typhi).

Causes, incidence, and risk factors:

The bacteria that cause typhoid fever -- S. typhi -- spread through contaminated food, drink, or water. If you eat or drink something that is contaminated, the bacteria enter your body. They travel into your intestines, and then into your bloodstream, where they can get to your lymph nodes, gallbladder, liver, spleen, and other parts of your body.

A few people can become carriers of S. typhi and continue to release the bacteria in their stools for years, spreading the disease.

Typhoid fever is common in developing countries, but fewer than 400 cases are reported in the U.S. each year. Most cases in the U.S. are brought in from other countries where typhoid fever is common.