The declining pattern of seroepidemiology of hepatitis A virus infection among adolescents in Bangkok, Thailand.

Hepatitis A virus (HAV) is a health problem in countries where seroepidemiology shows changes from hyperendemicity to intermediate endemicity. Throughout the last decade, we studied, in Bangkok, the seroprevalence of hepatitis A virus antibody (anti-HAV) among adolescents of different age groups. In 1996, 245 serum specimens from children aged between 10 and 19 were tested for anti-HAV by ELISA method. The results were compared to those obtained in 1987 and 1993 from students of the same age and attending the same school. Anti-HAV was detected in 31.4%, 14.6% and 12.7% of school children in the years 1987, 1993 and 1996, respectively. Each year, it was found that an increasing prevalence of anti-HAV was related to an increasing age. From 1987 to 1996, the age specific prevalence of anti-HAV was markedly decreased in younger children. The surveillance of the epidemiological trend of HAV infection is important for implementing preventive measures and for controlling the disease.