The earliest HIV-1 epidemic in China started in Yunnan province, which continues to be one of the most severe areas affected. While HIV-1 infections are spreading rapidly among injection drug users (IDUs) in China, sexual transmission of HIV-1 has also been confirmed, threatening the general population. Recent survey data indicated that heterosexual transmission of HIV-1 in Yunnan was steadily increasing. Diverse HIV-1 strains, including subtype B, C, CRF01, and CRF08, are circulating among individuals who acquired HIV through sexual contacts. Multiple HIV-1 subtypes, including subtypes B, C, and CRF08, were also detected among IDUs. In comparison with other IDU cohorts, intersubject env sequence variation was much higher among IDUs in Yunnan. Growing evidence suggests that unprotected sex continues to occur at high rates among IDUs and their sex partners. Intervention strategies are urgently needed to target individuals at high risk for HIV heterosexual transmission and injection drug use. The complex pattern of HIV-1 distribution in the high-risk populations in Yunnan may have important implications for HIV transmission as well as vaccine development and evaluation.
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