An epidemic of yellow fever in Central Brazil, 1972-1973. I. Epidemiological studies

An epidemic of jungle yellow fever occurred in Goias State, Brazil, between December 1972 and March 1973. Laboratory confirmed cases were observed in 36 counties located in the central and southern parts of the State. Seventy-one cases were proved, of which 44 were fatal. The diagnosis was made on the basis of pathology, serology, and virus isolation. Besides yellow fever, malaria and viral hepatitis were present, and in two fatal cases there was malarial pigment in the liver in addition to the specific lesions associated with yellow fever virus infection. The fact that male patients strikingly outnumbered females (9:1) and that young adults were predominantly affected indicates that transmission occurred mainly inside or adjacent to the forests. The lack of cases in urban areas can be attributed to the absence of Aedes aegypti in these areas. Yellow fever complement-fixing antibody in high titers was found in 18 of 1,201 (1.4%) persons living in eight counties of the affected area. This finding suggests that at least 21,000 persons out of the 1.5 million rural inhabitants of the three districts where the epidemic occurred had been infected by the virus. The epidemic subsided following an intensive vaccination campaign, and the last four cases were observed in March, 1973.