Epidemiology of hepatitis A and B in the Shanghai area: prevalence of serum markers.

Different population groups from the Shanghai area were surveyed by radioimmunoassay for serologic markers of previous infections with hepatitis A virus and hepatitis B virus. There were no significant differences in the prevalence of antibodies to hepatitis A virus (anti-HAV) in males and females, or in persons living in rural or urban areas. The prevalence of anti-HAV showed a biphasic increase with age, approaching 100% above age 50 years whereas the geometric mean titers declined. The rate of infection (attack rate) with hepatitis A among susceptibles in Shanghai declined appreciably between 1950 and 1960. The prevalence of hepatitis B markers also did not differ in the sexes, or in rural and urban populations. The patterns of prevalence of hepatitis B markers at different ages were compared to various theoretical mathematical models, and the data fitted best a model constructed from the assumption that two subpopulations of approximately equal size, one at low and the other at high risk, existed in the population groups studied. It was estimated that in Shanghai up to 12% of all individuals infected with hepatitis B became chronic hepatitis B surface antigen (HBsAg) carriers, although the overall prevalence of HBsAg carriers was only 6.9%. All HBsAg-positive individuals subtyped had been infected with hepatitis B virus of the subtype ad; 41.7% of HBsAg carriers also had hepatitis B e antigen (HBeAg), whereas in 32% of HBsAg carriers antibodies to HBe were present. Antibodies to HBsAg appeared to be lower in titer than in Western populations and to decline with age, and age-specific prevalence data indicated a relatively longer persistence of antibodies to hepatitis B core antigen.