Intra-familial transmission of Hepatitis B virus in a peri-urban community from the Democratic Republic of the Congo

Background. Despite global elimination targets set for 2030, Hepatitis B virus (HBV) infection remains a major public health challenge in low-income countries, including the Democratic Republic of Congo (DRC). Limited evidence on the regional transmission pathways preclude progress towards HBV elimination. This study aimed to assess the prevalence, molecular characteristics, and transmission dynamics of HBV in the Lukelenge health district, a peri-urban area in central DRC. Methods. We employed a two-tiered recruitment strategy: community member volunteers were enrolled during the first phase, and upon notification of HBV positivity in an index case, family contacts were subsequently recruited in the second phase. Participants were screened for hepatitis B surface antigen (HBsAg), followed by PCR amplification of HBV DNA and sequencing. Genotyping and phylogenetic analysis of preS/S sequences were performed to explore regional HBV diversity and transmission patterns. Results. A total of 751 participants from 677 households were included. The overall HBsAg prevalence was 3.8% [95% CI: 2.6–5.5], with the highest rate (10.1%) found in children aged 5 years and younger. All 42 HBV isolates belonged to genotype E, with 97.6% sharing the ayw4 serotype. Mutations with relevancy to immune escape were detected in 9.5% of strains, while those possibly linked to antiviral resistance were found in 4.7%. Maximum likelihood phylogenetic analysis showed intra-familial clustering of preS/S sequences, suggesting that parent-to-child transmission was the most frequent mode of HBV spread in the study population. Conclusions. HBV in Lukelenge shows intermediate endemicity, especially affecting young children. Intra-familial transmission revealed to be predominant, likely involving both vertical and horizontal pathways. Family-targeted interventions, including maternal screening and universal birth-dose vaccination, should be prioritized to eliminate HBV in this region.