This year’s Conference on Retroviruses and Opportunistic Infections offered a symposium on “Drivers of the HIV Epidemic and Potential Interventions.” Of surprise to many was the magnitude of the epidemic among men who have sex with men (MSM) in resource-poor nations, the extent to which it appears to be hidden, and how critical a refocusing on this high-risk group will be to contain the pandemic, internationally and nationally. Dr Frits van Griensven1 of the CDC discussed some key trends.1 In the United States, the overwhelming risk factor for acquiring HIV infection among women is heterosexual sex, accounting for 80% of those currently infected; 19% are infected through injection drug use (IDU). Among men, MSM remains the highest-risk group, at 67%. In terms of newly acquired infections, the incidence in the MSM group has been steadily rising in the United States: from 41% to 49% between 2001 and 2005. During this interval, the incidence of new HIV infection associated with other risk factors has remained stable or declined. There is a racial bias to these numbers. In 2005, new cases of HIV infection were attributed to MSM for 42% of white, non-Hispanic men; 36% of blacks; and only 19% of Hispanics. How much of this is related to underreporting, influenced by cultural restrictions, stigma, or other factors is unclear. As in the beginning of the national HIV epidemic, MSM must remain of paramount concern. The incidence of HIV infection among all US MSM is estimated to be between 1.9% and 3.6%, but in one urban cohort followed longitudinally, there was an 8% prevalence by age 20.1 In the absence of effective interventions, health officials predict a 38% prevalence for this cohort by age 40.1 For black MSM, the risk may even be greater. In one study, there was a 4% prevalence of HIV infection among black MSM in the United States aged 15 to 22 years. The projected prevalence for this group is 60% by age 40.1 The United States is not unique in this regard among resource-rich nations, despite widespread use of antiretroviral therapy and its potential to reduce viral loads and thus mitigate onward transmissions. For example, the transmission dynamics of HIV-1 among MSM has been followed in the Netherlands over the past 25 years. A mathematical model, validated by comparisons with actual observations over 4 different intervals, was used to calculate the reproduction number (R[t])-the average number of MSM infected by each HIV-positive MSM over his life span.2 It was estimated that 70% to 93% of all onward infections involved MSM who did not know their HIV status. The probable beneficial effect of widespread use of antiretroviral therapy on overall transmission was offset by an increase in risk behavior.2 These behaviors were not restricted to unprotected casual sex. “Serosorting”-the process of seeking a partner of like HIV status-has become an increasingly common tactic in an attempt to mitigate transmission among MSM.3,4 Yet it was associated with almost a quarter of all transmissions linked to unprotected anal intercourse with casual partners in Sydney, Australia, in 2005.3 This may relate to recent infections in the “window period” before seroconversion or most recent antibody test. In terms of viral load, this period has the greatest potential for viral spread, as documented by a study in Quebec from 1998 to 2005: 49.4% of all onward transmissions were attributed to persons with a primary HIV infection, defined as less than 6 months after seroconversion.5 Concerns are not limited to increased transmission of HIV among MSM. There is a high and increasing incidence of the types of human papillomavirus associated with squamous cell cancers isolated from the anus, penis, and mouth of MSM, with rates of 78%, 36%, and 30%, respectively, in a cohort from Barcelona.6 An MSM-specific transmission network for hepatitis C virus (HCV) infection has also been recognized in Amsterdam.7 This is disturbing because sexual transmission of HCV had traditionally been viewed as very inefficient at best and controversial, confounded by concurrent IDU.7 In the resource-poor world, where male-male sexual activity as a risk factor has been largely ignored, things do not appear to be much better. Accurate statistics are more difficult to come by; homosexuality is taboo in many nations of Africa and Asia.8 The prevalence of HIV infection among MSM in Mexico is estimated at 25.6%. It is 13.0% in Latin America. Statistics from the Joint United Nations Programme on HIV/AIDS for 2006 found a prevalence of HIV infection of 6.1% for all adults in Kilifi, Kenya, but it was 38.3% among MSM.1 Similar estimates were recorded from Dakar, Senegal (0.9% and 21.5%, respectively), and Khartoum, Sudan (1.6% and 9.1%). Hong Kong health officials recently reported a 4% prevalence of HIV infection among MSM and forecast a rise to 30% by 2020, unless focused prevention programs are instituted.9 A “concentrated epidemic” among any risk group-indicating a high susceptibility to future steep increases in transmission-is defined as a 5% prevalence.9 Equally disturbing were estimates of the fraction of a country’s total prevalence of HIV infection attributable to MSM via bisexual contacts. It ranged from 6.9% in Bejing, China, and 8.3% in Phnom Penh, Cambodia, to 37.5% in Yangon, Burma, and 30.3% in Bangkok, Thailand.1 Six years ago, CDC officials asked, “Are we headed for a resurgence of the HIV epidemic among men who have sex with men?”10 They suggested that we were “unless we act decisively to reevaluate, refocus, and reinvigorate our prevention efforts.”10 I have seen little evidence of such action in the United States or abroad. Two years after the CDC issued this caution-in the interval 2003 to 2004-the United States experienced an 8% increase in HIV/AIDS diagnoses among MSM.11 Twenty-six percent of sexually active MSM with AIDS in Los Angeles reported not using a condom in 2003, up from 11% in 2000.12 References: References1. van Griensven F. What’s driving the global MSM epidemic? 14th Conference on Retroviruses and Opportunistic Infections; February 25-28, 2007; Los Angeles. Abstract 55. 2. Bezemer D, de Wolf F, Boerlijst M, et al. Despite HAART, HIV-1 is once again spreading epidemically among men having sex with men in the Netherlands. 14th Conference on Retroviruses and Opportunistic Infections; February 25-28, 2007; Los Angeles. Abstract 151. 3. Mao L, Crawford JM, Hospers HJ, et al. “Serosorting” in casual anal sex of HIV-negative gay men is noteworthy and is increasing in Sydney, Australia. AIDS. 2006;20:1204-1205. 4. Laurence J. Report from the National HIV Prevention Conference. AIDS Reader. 2005;15:389-390. 5. Brenner BG, Roger M, Routy JP, et al; Quebec Primary HIV Infection Study Group. High rates of forward transmission events after acute/early HIV-1 infection. J Infect Dis. 2007;195:951-959. 6. Sirera G, Videla S, Piñol M, et al. High prevalence of human papillomavirus infection in the anus, penis and mouth in HIV-positive men. AIDS. 2006;20:1201-1204. 7. van de Laar TJ, van der Bij AK, Prins M, et al. Increase in HCV incidence among men who have sex with men in Amsterdam most likely caused by sexual transmission. J Infect Dis. 2007;196:230-238. 8. Akinsete OO, Sides T, Hirigoyen D, et al. Demographic, clinical, and virologic characteristics of African-born persons with HIV/AIDS in a Minnesota hospital. AIDS Patient Care STDS. 2007;21:356-365. 9. Lyn TE. New HIV infections among homosexuals up sharply in Hong Kong. Reuters. May 30, 2007. 10. Wolitski RJ, Valdiserri RO, Denning PH, Levine WC. Are we headed for a resurgence of the HIV epidemic among men who have sex with men? Am J Public Health. 2001;91:883-888. 11. Center for Disease Control and Prevention. Trends in HIV/AIDS diagnoses-33 states, 2001-2004. MMWR. 2005;54:1149-1153. 12. Laurence J. Yet another World AIDS Day. AIDS Reader. 2006;16:64-65.
