HEPATITIS-B VIRUS-INFECTION IN SINGAPORE

Although Singapore is in an endemic region for hepatitis B infection, the hepatitis B carriage rate of 5-6% is relatively low. The highest p ositivity rates for hepatitis B surface antigen (HBsAg) are found in t he paediatric age group, with another peak in 40-49 year olds. Studies suggest that, although perinatal transmission is an important route o f infection, most children acquire the virus through horizontal transm ission between family members. Viral replication continues at a high r ate in young carriers and tends to slow down with increasing age. Up t o 50% of hepatitis B carriers in Singapore have chronic hepatitis, sho wn by raised serum ALT values and liver histology, and about 10% are i nfected with the precore mutant virus. About 20% of carriers have cirr hosis. Among patients with HCC, up to 75% are HBsAg positive, of whom 45% are still viraemic. Mass vaccination against hepatitis B was intro duced into Singapore on a voluntary basis in 1983, with compulsory vac cination of babies born to HBeAg positive mothers since 1985. The numb er of cases of acute hepatitis B has fallen by 60% between 1989 and 19 95 although the problems of the longterm complications of chronic hepa titis B still need to be tackled.