Typhoid Fever

typhoid fever, also called typhoid, acute infectious disease caused by the bacterium Salmonella enterica serovar Typhi. The bacterium usually enters the body through the mouth by the ingestion of contaminated food or water, penetrates the intestinal wall, and multiplies in lymphoid tissue; it then enters the bloodstream and causes bacteremia.

Most major epidemics of typhoid fever have been caused by the pollution of public water supplies. Food and milk may be contaminated, however, by a human carrier of the disease who is employed in handling and processing them; by flies; or by the use of polluted water for cleaning purposes. Shellfish, particularly oysters, grown in polluted water and fresh vegetables grown on soil fertilized or contaminated by untreated sewage are other possible causes.

The prevention of typhoid fever depends mainly on proper sewage treatment, filtration and chlorination of water, and exclusion of carriers from employment in food industries and restaurants. In the early part of the 20th century, prophylactic vaccination using killed typhoid organisms was introduced, mainly in military forces and institutions, and contributed to a lowering of the incidence of the disease.