While in the United States and northern Europe, human herpesvirus 8 (HHV-8) appears to be mainly sexually transmitted with primary infection occurring in adulthood, the modes of transmission remain unknown in East and Central Africa, where Kaposi's sarcoma (KS) is a long-standing endemic disease, occurring not only in adults but also in children. The aim of our present study was to determine the prevalence of HHV-8 infection in children from Yaounde, Cameroon, Central Africa. Specific antibodies directed against both latent and lytic HHV-8 antigens were detected and titrated, with an immunofluorescence assay using the KS-1 cell line, in the plasma of 258 children and adolescents, of 32 mother and child pairs and of 189 pregnant women. Two different HHV-8 DNA-specific sequences were searched in the buffy coat by PCR assays. The overall HHV-8 seroprevalence was 27.5% among these children and adolescents. In newborns, seroprevalence reached 46%, reflecting passive transmission of maternal IgG. This was followed by a marked drop. Then, beginning around 4 years of age, a regular increase of HHV-8 antibodies took place, reaching 39% in the 12- to 14-year age group and 48% above 15 years, a rate similar (54.5%) to that observed in pregnant women. PCR detection of HHV-8 sequences was negative in seronegative children and positive in the buffy coat in 17% of HHV-8-seropositive children, reflecting a low viral load in the peripheral blood. Our results establish that in Central Africa HHV-8 infection takes place during childhood by casual routes, in contrast to the sexual transmission observed in adults in northern Europe and the United States. We hypothesize that the lymphadenopathic form of KS seen in African children is related to an early and massive infection by HHV-8 in susceptible individuals.