Risk Assessment: Tools, Techniques, and Their Applications

20.8 Typhoid Fever Example

The story of “Typhoid Mary” is the most commonly referred to tale of an asymptomatic carrier of a potentially deadly disease. Typhoid in and of itself is relatively difficult to spread without direct contact with a carrier, in the case of “Typhoid Mary.”

Typhoid fever is caused by Salmonella typhi. It affects human hosts only; it is spread through a fecal oral route. A vaccine is available to Americans traveling to endemic regions, oral live attenuated vaccine and an intravenous vaccine of the bacterial capsule. Approximately 4% of those infected with S. typhi become chronic carriers and will be completely asymptomatic (6). These carriers are then able to easily transmit the bacteria to others. These individuals can be treated with a short course of trimethoprim–sulfamethoxazole (TMP–SMX) but the efficacy of treatment is only 80%.

Eradication of typhoid fever is possible as the only current known reservoir is humans; however, sanitation and safe food handling practices would have to change worldwide.