The rate of new HIV infections in gay men in the UK has remained constant despite the introduction of HAART, according to a study published in the January 23rd edition of AIDS. Investigators believe that although the use of HAART has reduced infectivity, this has been offset by an increase in the amount of risky sex gay men are having. The investigators also express the belief that the large number of undiagnosed HIV infections amongst gay men, often accompanied by an inflammatory sexually transmitted infection (STI), is the main driving force behind the continuing HIV epidemic amongst UK gay men.
Using anonymous blood samples obtained from syphilis tests carried out on gay men attending fifteen sexual health clinics in the UK, investigators sought to estimate the incidence of new HIV infections between 1995 and 2001. They postulated that if the widespread use of HAART had significantly reduced the incidence of HIV infections amongst gay men, they would observe this in the gay men undergoing sexual health check-ups.
Information on age, known HIV infection, a current acute STI and whether the man was known to have AIDS accompanied each blood sample. The investigators also obtained national data on the uptake of HAART by gay men, AIDS deaths and diagnoses of gonorrhoea and syphilis between 1995 and 2001.
Blood samples were tested using the Serological Testing Algorithm for Recent HIV Seroconversion (STARHS). The use of this assay can determine the window period of HIV infection to within 133 days.
A total of 43,100 samples were collected between 1995 and 2001, and 3,565 were confirmed as HIV-positive. Of these, 1,645 were eligible for STARHS testing, of which 317 were deemed to be recent infections.
Overall, the investigators found “no significant upward or downward trend” in new HIV infections between 1995 and 2001. HIV incidence ranged between a high of 3.3% in 1996 and a low of 1.5% in 1999. New infections were highest in gay London STI clinic attenders, at a median of 3% annually, whereas median annual incidence outside London was a little under 1%.
Recent HIV infections were identified in all age groups, the highest incidence being in men aged between 35 – 44 in 1998, but in most years the highest incidence was amongst men aged 25 – 44.
Almost two thirds (n=1,154) of HIV infections identified through anonymous testing remained undiagnosed after the clinic visit, and 40% (n=462) had an associated acute STI.
Against this background of stable HIV incidence between 1995 and 2001, national data showed that the number of cases of gonorrhoea increased significantly from 1,836 in 1996 to 3,509 in 2001. In addition, there was a substantial increase in the number of cases of infectious syphilis diagnosed in gay men, increasing from a low of 30 cases annually between 1995 and 1997 to over 350 cases in 2001.
AIDS mortality fell substantially between 1995 and 1998 and has remained low since, and the investigators estimated that 95% of gay men with diagnosed HIV infection were receiving HIV care, with 60% taking HAART.
The investigators draw four important conclusions from these findings. First, “the most important finding is that the hope that the increasing use of effective combination ART since 1996 would lead to a significant reduction in the transmission of HIV has proved unfounded.” Second, “although HIV incidence has been greatest within London, incident infections have been found elsewhere throughout the study period.” Third, contrary to assumptions that new HIV infections were concentrated in younger gay men who had not absorbed the HIV prevention messages of the late 1980s and early 1990s, the investigators found that “recent HIV infections have been occurring at similar levels in [gay] men of all age groups between 20 and 44 years of age.”
Finally, the investigators conclude that the use of HAART has coincided with substantial increases in the rates of gonorrhoea and syphilis in gay men. “This suggests that among high-risk [gay] men, any fall in HIV transmission as a result of reduced infectivity due to ART has been offset by an increase in high-risk behaviour.”
The investigators suggest that the single most important factor driving the continuing HIV epidemic amongst UK gay men “may be the continuing existence of substantial numbers of undiagnosed HIV infections”, particularly as these are often accompanied by acute STIs.
Further information on this website
Bacterial STIs more common in gay men since HAART - news story
HIV incidence increasing most rapidly among older gay men in Amsterdam - news story
Both older and younger gay men having more unprotected sex in San Francisco - news story
High risk pool of gay men with multiple partners growing in UK - news story
Murphy G et al. HIV incidence appears constant in men who have sex with men despite widespread use of effective antiretroviral therapy. AIDS 18: 265 – 272, 2004.