Large-scale survey of hepatitis B virus infection in families.

To investigate HBV transmission in families on three islands in Okinawa, Japan, prevalence of HBV markers in two groups of inhabitants was determined. One group consisted of members of families in which there was at least one HBsAg carrier (carrier families); the other group consisted of members of families in which there were no HBsAg carriers (non-carrier families). A total of 3,261 serum samples were collected from subjects on Iriomote Island, Hateruma Island, and Yonaguni Island. These samples were tested for HBsAg by reversed passive hemagglutination (RPHA) and for antibody to hepatitis B core antigen (anti-HBc) by radioimmunoassay. Overall prevalences of HBsAg and anti-HBc were 8.2 and 65.8 per cent respectively. The prevalence of anti-HBC among members of carrier families (80.8%) was significantly higher than that among members of non-carrier families (61.6%) (P less than 0.001). The prevalence of anti-HBc among members of carrier families was higher in all age groups, and was particularly so in children. Within carrier families, the prevalence of anti-HBc was significantly higher in families in which there was at least one HBsAg carrier with HBeAg (94.5%) than in families with no HBeAg-positive carriers (76.1%). This difference was especially marked in young children. These data suggest that in families with HBsAg carrier(s), the risk of transmitting HBV to members, particularly to young children, is higher than in families without carriers, and that the risk is further increased in families with HBeAg-positive carrier(s).