BackgroundChina is experiencing a dynamic HIV/AIDS epidemic. While serology based surveillance systems have reported the spread of HIV/AIDS, detailed tracking of its transmission in populations and regions is not possible without mapping it at the molecular level. We therefore conducted a nationwide molecular epidemiology survey across the country.MethodsHIV-1 genotypes were determined from 1,408 HIV-positive persons newly diagnosed in 2006. The prevalence of each genotype was estimated by weighting the genotype’s prevalence from each province- and risk-specific subpopulation with the number of reported cases in the corresponding subgroups in that year.ResultsCRF07_BC (35.5%), CRF01_AE (27.6%), CRF08_BC (20.1%), and subtype B' (9.6%) were the four main HIV-1 strains in China. CRF07_BC and CRF08_BC were the primary drivers of infection among injecting drug users in northeastern and southeastern China, respectively, and subtype B' remained dominant among former plasma donors in central China. In contrast, all four strains occurred in significant proportions among heterosexuals nationwide, pointing to an expansion of the HIV-1 epidemic from high-risk populations into the general population. CRF01_AE also replaced subtype B as the principal driver of infection among men-who-have-sex-with-men.ConclusionsOur study provides the first comprehensive baseline data on the diversity and characteristics of HIV/AIDS epidemic in China, reflecting unique region- and risk group-specific transmission dynamics. The results provide information critical for designing effective prevention measures against HIV transmission.

Objectives:We sought to comprehensively analyze the origin, transmission patterns and sub-epidemic clusters of the HIV-1 CRF01_AE strains in China.Methods:Available HIV-1 CRF01_AE samples indentified in national molecular epidemiologic surveys were used to generate near full-length genome (NFLG) sequences. The new and globally available CRF01_AE NFLG sequences were subjected to phylogenetic and Bayesian molecular clock analyses, and combined with epidemiologic data to elucidate the history of CRF01_AE transmission in China.Results:We generated 75 new CRF01_AE NFLG sequences from various risk populations covering all major CRF01_AE epidemic regions in China. Seven distinct phylogenetic clusters of CRF01_AE were identified. Clusters 1, 2 and 3 were prevalent among heterosexuals and IDUs in southern and southwestern provinces. Clusters 4 and 5 were found primarily among MSM in major northern cities. Clusters 6 and 7 were only detected among heterosexuals in two southeast and southwest provinces. Molecular clock analysis indicated that all CRF01_AE clusters were introduced from Southeast Asia in the 1990s, coinciding with the peak of Thailand's HIV epidemic and the initiation of China's free overseas travel policy for their citizens, which started with Thailand as the first destination country.Conclusion:China's HIV-1 epidemic of sexual transmissions, was initiated by multilineages of CRF01_AE strains, in contrast to the mono-lineage epidemic of B′ strain in former plasma donors and IDUs. Our study underscores the difficulty in controlling HIV-1 sexual transmission compared with parenteral transmission.

To determine the origin and evolutionary history of two predominant and closely-related circulating recombinant forms (CRF07_BC and CRF08_BC), recombinant structures and phylogenies of 7 unique recombinant forms comprised of subtypes of B’ (Thai B linage) and C (designated URFs_BC) from archival specimens of injection drug users (IDUs) collected in 1996 to 1998 from western Yunnan and 4 circulating recombinant forms with B’/C recombinants recently identified (designated nCRFs_BC) in China were compared with those of CRF07_BC and CRF08_BC. The results showed that 5 of 7 URFs_BC and all the nCRFs_BC shared recombination breakpoints with CRF07_BC and/or CRF08_BC. Yunnan URFs_BC consistently occupied the basal branch positions compared with CRF07_BC, CRF08_BC, and nCRFs_BC in phylogenetic trees. The estimated most recent common ancestors (tMRCA) for Yunnan URFs_BC were from ~1987, approximately half a decade earlier than those for CRF07_BC (~1994) and CRF08_BC (~1992). Discrete phylogeographic and spatial diffusion analysis revealed that both CRF07_BC and CRF08 BC came from western Yunnan in the early 1990s. Our results provide compelling evidence for western Yunnan as the geographic origin of CRF07_BC and CRF08_BC, which emerged from a swarm of URFs_BC by a series of recombination events in western Yunnan in the early 1990s.