Molecular characterization of bat HBV and identification of HDV co-infection in Yunnan, China

Background Bats are natural reservoirs for Orthohepadnaviruses , but the diversity and evolution of bat hepatitis B viruses (BtHBVs) and their co-infection with bat hepatitis D virus (BtHDV) in China remain poorly understood. Methods In a molecular survey of bats from Yunnan Province, we detected BtHBV in 36.86% (129/350) of the samples, showing a notably high prevalence in Hipposideros pomona (41.75%). BtHDV co-infection was observed in 1.14% of BtHBV-positive bats. Results Genomic analysis of 18 BtHBV isolates revealed that all belong to the bat-specific Orthohepadnavirus Lineage V (BtHBV-7), yet exhibit measurable genetic divergence. We also characterized a highly divergent bat HDV strain, BtHDV-YNNJ49, which clusters within a distinct bat-associated deltavirus lineage but displays substantial genetic divergence from its closest relative, underscoring diversity within this lineage. Conclusions Collectively, our findings suggest that bats in Yunnan, particularly H. pomona , may act as natural hosts for both BtHBV and BtHDV. The identification of this divergent BtHDV strain expands our understanding of the genetic diversity and evolution of deltaviruses.