Definition of Typhoid fever:

Typhoid fever is a bacterial infection characterized by diarrhea, systemic disease, and a rash -- most commonly caused by the bacteria Salmonella typhi.

Causes, incidence, and risk factors:

S. typhi are spread by contaminated food, drink, or water. Following ingestion, the bacteria spread from the intestine via the bloodstream to the intestinal lymph nodes, liver, and spleen via the blood where they multiply.

Salmonella may directly infect the gallbladder through the hepatic duct or spread to other areas of the body through the bloodstream.

Early symptoms are generalized and include fever, malaise and abdominal pain. As the disease progresses, the fever becomes higher (greater than 103 degrees Fahrenheit), and diarrhea becomes prominent. Weakness, profound fatigue, delirium, and an acutely ill appearance develop.

A rash, characteristic only of typhoid and called "rose spots," appears in some cases of typhoid. Rose spots are small (1/4 inch) red spots that appear most often on the abdomen and chest. Typically, children have milder disease and fewer complications than adults.

A few people can become carriers of S. typhi and continue to shed the bacteria in their feces for years, spreading the disease, as in the case of "Typhoid Mary" in New York over 100 years ago.

Although typhoid fever is common in developing countries, less than 400 cases are reported in the U.S. each year, most brought in from abroad.