Epidemiology

Typhoid fever is spread by the fecal-oral route: Bacteria shed in the stool by infected persons can be ingested by someone else, usually through contaminated food or water.

Control of typhoid fever depends on maintaining a separation between sewage and drinking water. In certain areas of the world, as many as 3 percent of adults may be shedding S. typhi. Thus with poor sanitation, the population is continuously exposed, and the disease is constantly present. Such areas are termed endemic. Many of the least developed regions of the world are highly endemic for typhoid fever.

In contrast, where effective sanitation barriers are suddenly breached, transmission follows an epidemic pattern with a sudden rise in the incidence of a disease within a limited geographic area. For example, typhoid fever is almost unknown in Switzerland; yet contamination of Zermatt's water supply in 1963 resulted in 280 cases in a brief period of time. Ten years later, a similar compromise of the water supply of a migrant laborers' camp in Florida permitted an outbreak of 222 cases, with a single carrier as the apparent origin.

The other main vehicle for typhoid transmission is

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