| Abstract: | In a rural village in the Philippines, sera were collected from 744 residents and tested for evidence of hepatitis B virus infection. In the subsequent year, every household was visited every other week for a period of three months in an attempt to identify clinically apparent cases. At the end of the year, sera were obtained from 78% of persons initially negative for hepatitis B virus and 97% of those initially positive for hepatitis B surface antigen (HBsAg). Overall, HBsAg was found in 8.8% of the population tested, of whom 86% were still HBsAg-positive at the end of the year. Susceptibility to hepatitis B virus infection declined significantly with age, to only 16% in the age group 50 years and older. No difference in the prevalence of markers by sex was observed. The risk of infection in children appeared to increase if one or both parents were infected, compared with both parents susceptible (odds ratio = 3.3 and 7.6, respectively); the risk increased if older siblings were infected, compared with all older siblings susceptible. The overall incidence rate of hepatitis B virus infection was 3.3% per year. For those aged five years or younger, the incidence rate was 9.2%. None of the seroconverters manifested acute symptoms of infection. Despite the evident clustering in families of persons with hepatitis B virus markers, which is suggested by the prevalence survey, only two of nine incident infections observed were in children with HBsAg-positive close relatives. The findings support the impression that in countries endemic for hepatitis B virus, most new cases occur in the young and are clinically inapparent. Furthermore, screening families of young children for chronic carriers in an effort to identify children at high risk for hepatitis B virus infection would have a low sensitivity in the Philippine setting. |
