Hepatitis A sero-epidemiology in Singapore: a changing pattern.

Sera from 896 healthy volunteers between 15 and 56 years old were tested in 1987-1991 for immunoglobulin G antibody against the hepatitis A virus (IgG anti-HAV). The overall seroprevalence rate of IgG anti-HAV was 27%: it increased from 0.9% in the 10-19 years age group to 48.1% in the 40-49 years age group and was 100% in subjects over 50 years. There was no difference in anti-HAV seroprevalence between the sexes (29% among men and 26% among women) and races. A downward trend in anti-HAV seroprevalence was seen from 1987 (33%) to 1991 (21.4%). The level of exposure to the hepatitis A virus has decreased when compared with data obtained in 1975 and 1984-1985. Hepatitis A virus infection is no longer an infection of children and adolescents locally.