Phylogeographic Analyses Reveal a Crucial Role of Xinjiang in HIV-1 CRF07_BC and HCV 3a Transmissions in Asia

BACKGROUND: China faces an increasing prevalence of two HIV-1 circulating recombinant forms (CRFs) 07_BC and 08_BC. Both CRFs_BC were previously demonstrated to originate in Yunnan and spread to Liaoning from Yunnan via injection drug use (IDU) in China. Supposing it is true, we are unable to answer why only CRF07_BC, rather than both CRFs_BC together, was transmitted to Xinjiang. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the phylogeography of CRF07_BC and CRF08_BC using multiple HIV-1 genomic regions with Bayesian phylogeography method. Phylogenetic reconstructions showed that all CRF07_BC sequences were divided into two clades, Yunnan and Xinjiang, and all strains from other regions of mainland China clustered within the Xinjiang clade. Significant geographic diffusion links of Xinjiang with other regions (including Liaoning, Beijing, Jiangsu and Guangdong) were supported by Bayes factor tests. The temporal dynamics analyses showed that CRF07_BC spread from Xinjiang to Liaoning in 1996.10, and to Jiangsu in 2000.9. The analyses of CRF08_BC not only confirmed the previous conclusion on temporal and spatial dynamics of CRF08_BC, but also indicated that the CRF08_BC strains from Guangdong and Shanghai originated from Yunnan. The analyses of HCV 3a showed that it was introduced into Xinjiang in the early 1980s, and spread from Xinjiang to Yunnan in 1990.10 and to Jiangsu in 1999.2, and further from Yunnan to Guangxi in 1995.3. The temporal and spatial dynamics of HCV 3a were similar to some extent to that of HIV-1 CRF07_BC and/or CRF08_BC, suggesting a possible association in migration patterns between HCV and HIV-1 through IDU. In addition, HCV 3a spread from Xinjiang to Pakistan, implying a drug trafficking route linking them. CONCLUSIONS/SIGNIFICANCE: Xinjiang, as the most important transfer station for drug trafficking from Golden Crescent to other regions of China, plays a very crucial role in the transmission of viruses (e.g., HIV-1 and HCV) through IDU in Asia.