Rheumatic fever in Rochester, Minnesota, 1935-1978.

The incidence of rheumatic fever in the population of Rochester, Minnesota, during the years 1935 through 1978 was determined by means of the medical records-linkage system of the Rochester Epidemiology Program Project. The annual age-adjusted incidence rate per 100,000 population for all episodes of rheumatic fever was 9.7, comprising 7.0 for initial attacks and 2.7 for recurrent attacks. There was a marked decline over time: incidence rates of initial episodes decreased from 13.6 in 1935-1949 to 8.2 in 1950-1964 and 2.7 in 1965-1978; and rates of recurrent attacks decreased even more--from 7.0 to 3.2 and 0.3 in the same intervals. There was also a secular trend in the clinical manifestations of rheumatic fever, as the proportion of initial episodes with carditis increased from 23% in 1935-44 to 52% in 1965-1978.