The seroepidemiology of hepatitis in Papua New Guinea. II. A long-term study of hepatitis B.
Sera from 862 young children and 206 older subjects, living in four zones of the Sepik district in New Guinea, and obtained in March, August, December 1963, May 1964 and again in 1972, were tested for the hepatitis B virus (HBV) markers, surface antigen and antibody (HBsAg and anti-HBs) and core antibody (anti-HBc). This population was augmented by a group of adult women living at various altitudes in the Bismarck range area, upon whose sera the same tests were performed. There was a slight tendency for males to exceed females in HBV infections and in propensity to chronic carriage of HBsAg. HBV infections increased cumulatively with age in all ecologic zones studied, with no significant increase in prevalence after early adulthood. In the Sepik district, the HBV status of the population was relatively the same in 1963 and 1972. Overall, 64% of markers of HBV infection persisted over a nine-year period; anti-HBc was more persistent than anti-HBs. Most HBsAg positive subjects detected were chronic carriers, 74% of whom retained detectable antigen for a least nine years. The study provided no evidence to support the hypothesis that mosquitoes are important vectors of HBV. The proportion of HBV infected subjects with chronic HBsAg was about 15%, similar to that found in Caucasians in other studies. This casts some doubt on the theory that tropical populations are especially predisposed to chronic HBV infection.