Application of Hepatitis B Virus Genotyping and Phylogenetic Analysis in Intrafamilial Transmission of Hepatitis B Virus

Background. Infection with hepatitis B virus (HBV) in early life frequently results in persistent infection, and clustering of the chronic infection within a family is common. However, the relative contribution of perinatal mother-to-infant transmission or early horizontal transmission to the intrafamilial clustering of HBV infection remains unclear. Therefore, we used HBV genotyping and phylogenetic analysis to elucidate the modes of intrafamilial HBV transmission in Taiwan. Methods. HBV genotypes and serological markers were determined for 103 individuals from 20 families with evidence of clustering HBV infection. Results. Three patterns of intrafamilial clustering of HBV infection were identified. Among the 20 families, 8 included a hepatitis B surface antigen (HBsAg)-positive mother (pattern I), 7 included an HBsAg-positive father (pattern II), and in the remaining 5, both parents were positive for HBsAg (pattern III). The rates of HBsAg positivity for children of the 3 representative groups of families were 85.7%, 65.4%, and 87. 5%, respectively (P = .16). The identical genotyping results between index parent and carrier children indicated that pattern I clustering was caused by maternal transmission, whereas pattern II clustering was caused by paternal transmission. In pattern III clustering, a concordant HBV genotype between carrier children and mother or father was found in 3 and 2 families, respectively. The modes of transmission were confirmed by phylogenetic analysis in 1 family of each pattern. Conclusions. In Taiwan, maternal and paternal transmissions are both important in the intrafamilial spread of HBV infection