| AIDS, caused by the human immunodeficiency virus (HIV) infection, has caused serious public health problem. Globally, a large of population have infected with HIV-1 although its infection rate is still low in China. Yunnan was considered not only the epicenter of HIV-1 prevalence in China, but also the hotspot where HIV-1 recombinants developed. CRF07_BC and CRF08_BC, which is the main CRFs of subtype B and C circulating in most region of China, was also origined in Yunnan. Due to its special geographic location, Yunnan was considered as the communicating hub between China and Southeast Asian countries, which was major reason for Yunnan becoming the epicenter of HIV-1 prevalence and furthermore the origin place of circulating HIV-1 subtypes and CRFs in Asia. As the "bridge population" cross-border travelers have act as the important media for HIV-1 cross-border transmission. Huge cross-border population and more than 4,000 km borderline have brought a great challenge to monitoring and prevention of HIV infection.In current study,280,961 entry travelers were recruited at land ports located in 7 bordering prefectures respectively, for HIV-1 screening in the Yunnan Province between 2003 and 2012. Of them,2380 were determined as HIV-1 positive with infection rate of 0.85%. The HIV-1 infection rate showed a decreasing trend overall. Travelers entering at Dehong port had the highest HIV-1 infection rate (5.12%), followed by those entering at Baoshan (0.88%), Lincang (0.83%), and Honghe (0.71%). For all HIV-1 positive cases, travelers aged 21-30 and 31-40 years were the most commonly infected individuals, accounting for 38.45% and 37.77% of all cases, respectively. Phylogenetic analysis on sequences gag-pol gene (809 bps) showed that CRF01_AE (46.23%) and CRF08_BC (17.8%) were the main circulating subtypes, followed by subtype C (8.41%), CRF07_BC (2.47%), other B/C recombinants and undefined genotypes. The infection rate of CRF01_AE subtype was stability and sustained growth; the proportion of CRF08_BC in each year was about 15%, declining in recent years; as the major epidemic subtype in China in Yunnan region ever subtype B and C, in the past ten years has been the change of the crowd to maintain lower infection rate, and has a tendency to decrease year by year.Furthermore, phylogenetic and evolutionary characteristics of the major circulating subtypes were analyzed. It was showed that strains form recruited travelers and the endemic strains in Yunnan, or those from boring regions have the close genetic relationship. No obvious phylogenetic independence was observed between these strains from different population. This indicated inseparable relationship among the strains from this population and local population in boring areas, and might further prove this population is playing key role in promoting cross-border transmission in Yunnan province.This research was characterized with geographic specific, the long period of sample collecting. HIV-1 cross-border transmission and its evolution have been well reflected by our findings. It is also possible to discover the novel genotype/recombinant. Our findings may provide the epidemiological data for the monitoring on HIV cross-border transmission, and is helpful for clarifying its evolution and forecasting on HIV spread. |
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