Salmonella typhi infections in the United States, 1975-1984: increasing role of foreign travel.

To explore changes in the epidemiology of typhoid fever in the United States, cases reported to the Morbidity and Mortality Weekly Report (MMWR) and typhoid case report forms submitted by state and local governments are reviewed. The incidence of typhoid fever in the United States fell from one case per 100,000 population in 1955 to 0.2 cases per 100,000 in 1966 and has since remained fairly stable. Review of case report forms for 2,666 cases of acute typhoid fever that occurred between 1975 and 1984 showed that 62% were imported, in contrast to only 33% during 1967-1972. The proportion of cases imported has continued to rise, reaching 69% in 1984. The major sources of the 1975-1984 cases were Mexico (39%) and India (14%). The case-fatality rate was 1.3%. Antimicrobial resistance was a minor problem, and large outbreaks were unusual. Further decline in the incidence of typhoid fever in the United States probably must await the advent of an effective vaccine with minimal adverse effects for use by travelers.