EPIDEMIOLOGIC PATTERNS OF HEPATITIS-B VIRUS (HBV) IN HIGHLY ENDEMIC AREAS

This paper uses meta-analysis of published data and a deterministic ma thematical model of hepatitis B virus (HBV) transmission to describe t he patterns of HBV infection in high endemicity areas. We describe the association between the prevalence of carriers and a simple measure o f the rate of infection, the age at which half the population have bee n infected (A(50)), and assess the contribution of horizontal and peri natal transmission to this association. We found that the two main hyp er-endemic areas of sub-Saharan Africa and east Asia have similar prev alences of carriers and values of A(50), and that there is a negative nonlinear relationship between A(50) and the prevalence of carriers in high endemicity areas (Spearman's Rank, P = 0.0086). We quantified th e risk of perinatal transmission and the age-dependent rate of infecti on to allow a comparison between the main hyper-endemic areas. East As ia was found to have higher prevalences of HBeAg positive mothers and a greater risk of perinatal transmission from HBeAg positive mothers t han sub-Saharan Africa, though the differences were not statistically significant. However, the two areas have similar magnitudes and age-de pendent rates of horizontal transmission. Results of a simple compartm ental model suggest that similar rates of horizontal transmission are sufficient to generate the similar patterns between A(50) and the prev alences of carriers. Interrupting horizontal transmission by mass immu nization is expected to have a significant, nonlinear impact on the ra te of acquisition of new carriers.