Emerging HIV infections with distinct subtypes of HIV-1 infection among injection drug users from geographically separate locations in Guangxi Province, China

Heroin users from Guangxi province, a southern province of China that borde rs Vietnam in the south and Yunnan province in China in the west, were stud ied for prevalence and risk factors for HIV-1 infection. Viral env sequence s from HIV-1-positive individuals were also determined for subtypes of HIV- 1. The overall HIV prevalence among 227 heroin users was 40%. Most had used drugs for less than or equal to 3 years. Sharing of injection equipment an d unprotected sex were significantly associated with HIV-1 infection. Subty pes C and E HIV-1 were detected in infected heroin users and were sharply s egregated in two geographic locations: only subtype C was found in a border city with Yunnan province, whereas only subtype E was found in a city bord ering northern Vietnam. HIV-1 strains within each subtype were remarkably h omogenous, with a mean intersubject DNA distance of 2.32% for subtype E and 1.13% for subtype C, respectively. Phylogenetic analysis of C2-V5 region o f Guangxi subtype E env sequences revealed significant clustering with subt ype E sequences from southern Vietnam and Cambodia. These results suggest t hat HIV-1 infection among heroin users in Guangxi represents two emerging e pidemics initiated from distinct sources: one from Vietnam and another from Yunnan province. Factors associated with HIV-1 infection were not restrict ed to injection practices. Unprotected sexual behaviors are likely to incre ase the probability of HIV transmission beyond this high-risk population. D esigning and implementing effective intervention strategies targeted toward both injection drug use and high risk sexual behavior are urgently needed to further reduce HIV-1 spread in China.