Hepatitis A virus : Declining seroprevalence in children and adolescents in Southeast Asia

This article reviews age-related seroprevalence of hepatitis A virus (HAV) in a number of Southeast Asian countries and highlights how these patterns have changed over the recent decades. The prevalence of HAV in a country largely reflects its standards of hygiene and socioeconomic conditions. Countries that undergo socioeconomic development show a major change in HAV prevalence from high to low endemicity and this is largely reflected in patterns of age-related seroprevalence. Countries like Singapore Thailand and Malaysia have experienced a decline in childhood and adolescent HAV seroprevalence typical of countries that undergo socioeconomic development. By contrast India has remained a country of high endemicity with almost universal seroconversion in childhood. The Philippines and Vietnam show age-related seroprevalence patterns typical of high to moderate endemicity while Indonesia shows significant regional variation in HAV seroprevalence. Populations within countries that exhibit major improvements in endemicity and age-related HAV seroprevalence patterns are at risk of HAV epidemics and a paradoxical increase in incidence tends to occur as seroconversion shifts from children to adults. Vaccinations could prove to be a public health measure of considerable benefit for Southeast Asian countries experiencing improved age-related HAV seroprevalence patterns in parallel with socioeconomic development.