LAUSR

Extraordinary HIV-1 recombination is occurring in China. Here, a novel second-generation circulating recombinant form (CRF174_0708) was found in Yunnan Province, China. First, Bootscanning revealed a mosaic structure with three subtype B segments inserted into a subtype C backbone. However, phylogenetic analysis showed that subregions 2B (2978–3267) and 4B (6023–6196) were related to CRF07_BC, whereas subregion 6B (8846–8997) was related to CRF08_BC, suggesting that the sequences could be recombined from CRF07_BC and CRF08_BC. Furthermore, Bootscanning-guided partitioning with subregion-specific phylogenetic analysis confirmed that subregions I (790–1902), III (2636–3746), V (4327–5825), VII (6023–6196) and IX (6379–6782) from CRF07_BC, and subregions II (1903–2635), IV (3747–4326), VI (5826–6022), VIII (6197–6378) and XI (7463–9512) from CRF08_BC. Bayesian dating traced the emergence to 2005–2007, consistent with the expansion of the parental strains. This discovery advanced our understanding of HIV-1 evolution.