PREVALENCE OF MARKERS OF HEPATITIS-B VIRUS-INFECTION IN VARIOUS COUNTRIES - A WHO COLLABORATIVE STUDY

Abstract

A WHO collaborative study on viral hepatitis B in which 21 laboratories in 20 countries participated is described. The prevalence of hepatitis B surface antigen (HBsAg), its subtypes and its antibody (anti-HBs) were defined by age and sex and urban or rural residence in normal populations in different parts of the world. High-risk groups in the populations and patients with various diseases were also investigated. HBsAg and anti-HBs prevalence rates were higher in African and Asian countries than in the Americas, Australia and northern and central Europe. Some eastern and southern European countries had high HBsAg and anti-HBs prevalence rates comparable with those in Africa and Asia. In countries with low HBsAg and anti-HBs prevalence, there seems to be a gradual build-up during late childhood or early adolescence; in countries with high HBsAg and anti-HBs prevalence, they were frequently detected in preschool children. Although the trend was towards a higher frequency of HBsAg and anti-HBs in urban than in rural and in male than in female populations, the differences were in most cases not significant. A significantly higher prevalence of markers of hepatitis B virus infection was seen in high-risk population groups than in normal populations. This was clearly defined only in areas with low HBsAg and anti-HBs prevalence in the normal population. The geographical distribution of HBsAg subtypes showed a higher prevalence of the ad subdeterminant over ay in central European countries; in eastern and southern Europe, the ay subtype predominated. In West Africa, ayw was the only variant found; in East Africa, ad occurred more frequently than ay. In Australia, both adw and ayw subtypes were detected; in the Far East and southeast Asia, only adw and adr were seen.