Identification of an Emerging HIV-1B/C Circulating Recombinant Form (CRF176_BC) in Heterosexual Populations in Yunnan Province, China.

The current HIV-1 epidemic in China is characterized by the co-circulation of multiple subtypes and recombinant forms. A novel circulating recombinant form of HIV-1 (CRF176_BC) has been identified in Yunnan Province, China. Near-full-length genome sequences were obtained from four individuals who identified as heterosexual and were epidemiologically unlinked. Phylogenetic analysis revealed that these sequences formed a distinct monophyletic cluster from known subtypes and CRFs. Bootscanning analyses revealed a subtype C backbone with two subtype B insertions. Bayesian evolutionary dating estimated that the four genomes shared a common ancestor between 2014 and 2016, which was not far from the present. Unlike earlier CRF_BCs, which were associated with injecting drug use in the 1990s, the emergence of CRF176_BC indicates a shift toward sexual transmission. This finding emphasizes the continuous evolution of HIV-1 in Yunnan, driven by co-circulating lineages and evolving transmission dynamics. It also highlights the importance of targeted surveillance in informing public health strategies in the context of evolving epidemics.