Three per cent of men who have sex with men HIV-positive in Beijing

Researchers from China and the USA suggest in this week's issue of The Lancet that men who have unprotected sex with men might worsen China's emerging HIV-1 epidemic because they form a sexual bridge between men and women.

In particular, they found that the group of men who were most likely to be HIV-positive were also the group most likely to have been married (OR 2.98, 95% CI 0.99-8.98). Men who had ever had sex with a woman showed a trend towards a higher risk of HIV infection (OR 2.69, 95% CI 0.63 – 8.16).

However, the HIV prevalence found among men who have sex with men in Beijing (3.1%) is considerably lower than the HIV prevalence noted in other, classic `bridging` groups. Sentinel surveillance in China has revealed that 50-70% of injecting drug users at some sites are HIV-positive. Up to 5% of female commercial sex workers are HIV-positive. China is undergoing a serious HIV-1 epidemic in intravenous drug users, sex workers, and former blood donors-the UN estimates that as many as 10 million people could be infected by 2010.

Although 75% of current infections are from intravenous drug use and infected blood transfusions, sexual transmission could become the predominant mode of transmission. In China, an estimated 2-8 million men have sex with other men, and might play a key part in spreading infection. Kyung-Hee Choi from the Center for AIDS Prevention Studies, San Francisco, USA, and colleagues assessed rates of HIV-1 infection and risk behaviour of such men in Beijing, China.

The investigators recruited participants through informal social networks and in bars, parks, and bath-houses frequented by men who have sex with men. Health-care workers took a sample of fluid from the mucous membranes of the mouth to test for HIV-1. Samples that tested positive were confirmed by blood tests.

Of 481 men, 15 tested positive for HIV-1. Half of all men reported unprotected intercourse with men during the 6 months before the study, and almost a quarter had unprotected anal or vaginal intercourse with women during the same period. Prevalence of infection was 4.5 times higher in men older than 39 years than in those younger, and many more older men had been married (64%) than had younger men (11%).

Dr Choi comments: "There is low but significant HIV-1 prevalence in men who have sex with men in Beijing. However, in view of the high rates of unprotected sex in such men, HIV-1 infection rates will continue to rise unless prevention measures are implemented. These findings suggest that men who have sex with men could potentially serve as a sexual bridge between high-risk men and low-risk women, and this sexual mixing pattern might contribute to the sexual transmission of HIV-1 to heterosexually active adults."