Abstract
The prevalence of CRF07_BC is 39.7% and has become the most infectious HIV strain in China. To study the transmission and diffusion trajectory of CRF07_BC in China and to prevent further expansion of its transmission. A total of 16,635 sequences of the CRF07_BC pol gene were collected from 1997-2020. We characterized the gene subtypes according to a phylogenetic tree analysis. A 0.50% molecular network was constructed to analyze the transmission relationship among different provinces for CRF07_BC and its two epidemic clusters. Spatial and temporal propagation characteristics were analyzed according to phylogeographic analysis. Finally, we evaluated the differences in transmission of CRF07_BC-O, and CRF07_BC-N. Our dataset included 8,816 sequences of CRF07_BC-N and 7,819 sequences of CRF07_BC-O. There were 7,132 CRF07_BC sequences in the molecular network, and the rate of clustered was 42.9%. Compared to CRF07_BC-O, CRF07_BC-N showed significantly (P<0.001) higher transmission-specific rates. CRF07_BC originated among injecting drug users (IDUs), and spread to men who have sex with men (MSMs) and heterosexual individuals (HETs), while MSMs also transmitted directly to HETs. CRF07_BC-O and CRF07_BC-N were prevalent in Xinjiang and Sichuan, respectively, before spreading interprovincially. In modern China, CRF07_BC-N occurs in five of the major economic zones. The CRF07_BC strain, which has contributed to the highest number of HIV infections in China, is divided into two epidemic clusters. Compared with CRF07_BC-O, risk of transmission is much greater in CRF07_BC-N, which is predominantly prevalent in economically developed provinces, and both MSMs and IDUs have transmitted this epidemic cluster to HETs. High-resolution, large-scale monitoring is a useful tool in assessing the trend and spread of the HIV epidemic. The rapidly developing economy of China requires an equally rapid response to the prevention and control of infectious diseases.
Highlights
CRF07_BC was initially characterized among HIV positive among injecting drug users (IDUs) in 1996 and is one of the most predominant Circulating Recombinant Forms (CRFs) of HIV strains in China (1–3)
We evaluated the differences in transmission between two CRF07_BC epidemic clusters in China by the rate of clustered, network density (ND), and rate of interprovincial transmission (RIPT), respectively
By phylogenetic tree analysis (See reference 9 for the phylogenetic trees), we identified that the dataset consisted of 53.0% (8,816/16,635) CRF07_BC-N sequences and 47.0% (7,819/ 16,635) CRF07_BC-O sequences (Table 1)
Summary
CRF07_BC was initially characterized among HIV positive among injecting drug users (IDUs) in 1996 and is one of the most predominant Circulating Recombinant Forms (CRFs) of HIV strains in China (1–3). The HIV subtype B' strain from Thailand spread to Yunnan around 1985 (4). In 1989, the HIV subtype C strain from India spread to Yunnan (5–7). CRF07_BC was formed by recombination of subtype B' from Thailand and subtype C from India and has spread to many provinces in less than 30 years. CRF07_BC-O was genetically and epidemiologically similar to the original CRF07_BC, circulating in IDUs and heterosexual individuals (HETs). It was called CRF07_BC-unclustered or CRF07_BCOthers in some studies (9–11). CRF07_BC-N is the latest cluster derived from CRF07_BC-O and has mostly been reported in men who have sex with men (MSM) It has been called CRF07_BCCluster 1 or CRF07_BC-MSM in some studies (9–11)
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