Secular trend and geographical variation in hepatitis A infection and hepatitis B carrier rate among adolescents in Taiwan: an island-wide survey.

During the last two decades an economic boom has occurred in Taiwan, a region where the prevalence of both hepatitis A and B virus infection was formerly very high. To examine the impact of socioeconomic developments on the secular trend and geographical variation in hepatitis A and B virus infection, 875 adolescents selected randomly from 20 junior high schools were studied. Serum samples collected from the subjects were tested for hepatitis A antibody (anti-HAV) and hepatitis B surface antigen (HBsAg) by enzyme immunoassay using commercial reagents. The anti-HAV prevalence increased from northern through central to southern Taiwan; the prevalence was highest in aboriginal townships and lowest in metropolitan precincts. This striking variation in anti-HAV prevalence in different geographical locations and at different urbanization levels remained significant in multiple logistic regression analysis. The HBsAg prevalence was significantly higher in aboriginal townships than in rural and urban townships and metropolitan precincts. In addition, HBsAg prevalence was related inversely to the number of physicians per 1,000 population. The prevalence of both anti-HAV and HBsAg declined significantly during the last decade in Taipei City and County. The decrease in anti-HAV prevalence may be due to improvements in environmental hygiene, water supply, and food sanitation, while the decline in the HBsAg carrier rate may result from the use of disposable needles and syringes as well as screening for HBsAg in blood banks.