REEMERGENCE OF YELLOW-FEVER IN SENEGAL IN 1995

An outbreak of yellow fever (YF) occurred in the central part of Seneg al during October 1995. Thirty-one probable cases were detected and 79 cases were confirmed either by IgM ELISA or by virus isolation (30 st rains isolated). The case fatality rate was 18.9%. incidence of the in fection was evaluated by a serosurvey in the area. Males 10-29 years o ld belonging to the Peul ethnic group were more affected. Moreover, 28 YF virus strains were isolated from mosquitoes and larvae pools and v ertical transmission of YF virus by Aedes aegypti was also demonstrate d for the first time in the field. This outbreak occurred after the ma jor amplification of the wild cycle of YF virus in 1993 in West Africa . This epidemic represented a typical example of intermediate transmis sion of YF: both humans and wild vertebrates are involved in the virus cycle through wild mosquitoes with semidomestic habits, mainly Ae. fu rcifer, Ae. luteocephalus, and domestic vector Ae. aegypti. It was con trolled by a prompt immunization campaign. The impact of inclusion of YF vaccine in the Expanded Program of Immunization, which has been con ducted in Senegal for eight years, is discussed.