Typhoid Fever is transmitted by eating food or drinking beverages improperly handled by an infected person with Salmonella Typhi or if contaminated water containing the bacteria is used to for washing food or drinking.
Unlike other Salmonella-related infections, where a range of animals can become infected and act as reservoirs for the bacteria, humans are the sole source of infection for Typhoid Fever. Of those infected, 10% of untreated cases can shed the bacteria in their feces or urine for up to 3 months and a smaller percentage can become asymptomatic carriers for a year or longer. Both ill and asymptomatic people can carry the bacteria in their blood or gastrointestinal tract and act as a source of infection to others by shedding the bacteria in their feces and sometimes in urine.
Contaminated drinking water is more common in countries without adequate sewage and sanitation treatment. Most cases of Typhoid Fever reported in the United States are travel-related. Countries where travelers from the United States have been most at risk of acquiring Typhoid Fever include those throughout Asia, Latin America and Africa.
Common sources of infection in areas of the world at risk include:
- Drinking water and beverages contaminated with human waste – untreated tap water ingested directly, used to make ice or roadside drinks, or swallowed during teeth brushing or showering
- Raw fruits and vegetables – rinsed or washed with untreated water sources or handled by an infected food handler
- Shellfish, such as oysters, clams, scallops and mussels – contamination can occur when harvest beds are exposed to human waste in untreated water runoff