Outbreaks of typhoid fever in the United States, 1960-99.

Although the incidence of typhoid fever in the United States has been low since the 1940s, Salmonella Typhi continues to cause outbreaks. We reviewed reported outbreaks of typhoid fever from 1960 to 1999. There were 60 outbreaks; in 54, exposure occurred within the United States. These 54 outbreaks accounted for 957 total cases (median 10) and 4 deaths. In 36 (67%) outbreaks the route of transmission was identified, and in 16 (62%) of the 26 foodborne outbreaks an asymptomatic carrier was identified by culture or serology. The median incubation period was 2 weeks. Isolates from 10 (40%) of 25 outbreaks were phage type E1. The average frequency of outbreaks decreased from 1.85/year during 1960-79 to 0.85/year during 1980-99 (P=0.0001). S. Typhi outbreaks in the United States are generally small in size but can cause significant morbidity, and are often foodborne, warranting thorough investigation.