Determinants of HIV seroconversion among men who have sex with men living in a low HIV incidence population in the era of highly active antiretroviral therapies

Evolving the gay, bisexual and other men who have sex with men time-based deferral to sexual risk screening for all donors: The contribution of Canadian research programmes

BACKGROUND AND OBJECTIVES

In Canada, the time deferral for gay, bisexual and other men who have sex with men (gbMSM) to donate blood has gradually decreased. In September 2022, this deferral was replaced with sexual behaviour-based screening for all donors. We investigate how data from targeted research programmes addressed knowledge gaps to support this change.

MATERIALS AND METHODS

We conducted a scoping review describing the Canadian literature available before the research programmes relating to (1) behavioural indicators of HIV risk and (2) attitudes to blood donation among gbMSM, current donors and the general population. We summarize the targeted research programmes, their outputs and impact to date.

RESULTS

For question 1, five projects met inclusion criteria. For question 2, three articles met inclusion criteria. Knowledge gaps identified were insufficient evidence of HIV incidence in gbMSM who met other donor eligibility criteria and scant data on opinions and views of blood donation and screening criteria for sexual risk behaviours. The research programmes funded 19 projects at 11 different research sites involving over 100 individual researchers/collaborators resulting in 19 peer-reviewed publications to date. Leveraging existing gbMSM cohorts yielded relevant HIV incidence data to inform safety modelling studies. Findings indicated that sexual behaviour-based screening was acceptable to gbMSM and donors, and donor discomfort around specific questions could be mitigated with clear explanations.

CONCLUSION

Targeted research programmes filled critical knowledge gaps and informed a change to gender-neutral, sexual behaviour-based screening for all donors. Findings supported successful implementation of these changes with research-informed staff training.

Sexual Behavior Transition and Acute and Early HIV Infection Among Men Who Have Sex With Men: Evidence from an Open Cohort in China, 2011-2019

The present study examined how sexual behaviors transit over time among men who have sex with men (MSM) and whether these transitions were associated with acute and early HIV (AEH) infection. An open cohort study was conducted using snowball sampling to recruit MSM via physical venues and Internet venues from 2011 to 2019, in China. Cox models were used to estimate the correlates of risk factors and AEH infection. We used Latent Transition Analysis (LTA) to describe behavioral profile and explore latent behavioral "trans-phenotypes," then examined the effect between different "trans-phenotypes" and AEH infection risk and explored the effect of characteristics as possible predictors of sexual behavior transition. Of 6502 MSM, a total of 1974 individuals with negative human immunodeficiency virus (HIV) tests at baseline and at least 2 visit records were included in the final analysis from 2011 to 2019. During an average 1.84 years of follow-up, 64 AEH infections were documented. In the multivariable Cox model, the association between condom use in last anal sex (HR: 0.095, 0.038-0.205), fewer sexual partners (HR: 0.375, 0.205-0.712), low frequency of condom use (HR: 3.592, 1.186-11.272), and AEH acquisition were found. The percentage of MSM with "maintain/develop safety-profile," "consistent risky-profile," and "safety-profile to risky-profile" were 52.48, 40.17, and 7.35%, respectively. Compared with "maintain\develop safety-profile," "consistent or develop risky-profile" had an increasing likelihood of AEH infection. Meanwhile, male sex workers (MSWs) or older MSM were more likely to consist or transit in "risky-profile." Having middle education is a risk factor to transit in "risky-profile" for MSM with "safety-profile" at baseline. In addition, MSM who accept health services in the past year engaged in higher proportion of developing safety-profile. Approximately half of MSM maintain or develop risky behavior with the increasing likelihood of AEH acquisition in China, which suggested that targeted and intensive interventions should be prioritized to maintain safety-profile. Clinical Trial Number: ChiCTR2000039500.

Different guidelines for pre-exposure prophylaxis (PrEP) eligibility estimate HIV risk differently: an incidence study in a cohort of HIV-negative men who have sex with men, Portugal, 2014-2018

IntroductionGuidelines for pre-exposure prophylaxis (PrEP) provide criteria to identify individuals at higher risk of HIV infection. We compared the ability to predict HIV seroconversion of four guidelines: the World Health Organization (WHO), the United States Public Health Service and Centers for Disease Control and Prevention (US CDC), the European AIDS Clinical Society (EACS) and the Portuguese National Health Service (PNHS).AimWe aimed to measure the association between guideline-specific eligibility and HIV seroconversion.MethodsWe studied 1,254 participants from the Lisbon Cohort of men who have sex with men with at least two evaluations between March 2014 and March 2018, corresponding to 1,724.54 person-years (PY) of follow-up. We calculated incidence rates (IR) according to each guideline eligibility definition and incident rate ratios (IRR) to test the association between eligibility at baseline and HIV seroconversion.ResultsWe found 28 incident cases (IR: 1.62/100 PY; 95% confidence interval (CI) 1.12-2.35). Guidelines' sensitivity varied from 60.7% (EACS) to 85.7% (PNHS) and specificity varied from 31.8% (US CDC) to 51.5% (EACS). IR was highest among those defined as eligible by the PNHS guideline (2.46/100 PY; IRR = 4.61; 95% CI: 1.60-13.27) and lowest for the WHO guideline (1.89/100 PY; IRR = 1.52; 95% CI: 0.69-3.35).ConclusionsBeing identified as eligible for PrEP was associated with a higher risk of infection. The magnitude of risk varied according to the guideline used. However, the number of HIV infections identified among ineligible participants highlights the potential for missing people who need PrEP.

Expert consensus statement on the science of HIV in the context of criminal law

INTRODUCTION

Globally, prosecutions for non-disclosure, exposure or transmission of HIV frequently relate to sexual activity, biting, or spitting. This includes instances in which no harm was intended, HIV transmission did not occur, and HIV transmission was extremely unlikely or not possible. This suggests prosecutions are not always guided by the best available scientific and medical evidence.

DISCUSSION

Twenty scientists from regions across the world developed this Expert Consensus Statement to address the use of HIV science by the criminal justice system. A detailed analysis of the best available scientific and medical research data on HIV transmission, treatment effectiveness and forensic phylogenetic evidence was performed and described so it may be better understood in criminal law contexts. Description of the possibility of HIV transmission was limited to acts most often at issue in criminal cases. The possibility of HIV transmission during a single, specific act was positioned along a continuum of risk, noting that the possibility of HIV transmission varies according to a range of intersecting factors including viral load, condom use, and other risk reduction practices. Current evidence suggests the possibility of HIV transmission during a single episode of sex, biting or spitting ranges from no possibility to low possibility. Further research considered the positive health impact of modern antiretroviral therapies that have improved the life expectancy of most people living with HIV to a point similar to their HIV-negative counterparts, transforming HIV infection into a chronic, manageable health condition. Lastly, consideration of the use of scientific evidence in court found that phylogenetic analysis alone cannot prove beyond reasonable doubt that one person infected another although it can be used to exonerate a defendant.

CONCLUSIONS

The application of up-to-date scientific evidence in criminal cases has the potential to limit unjust prosecutions and convictions. The authors recommend that caution be exercised when considering prosecution, and encourage governments and those working in legal and judicial systems to pay close attention to the significant advances in HIV science that have occurred over the last three decades to ensure current scientific knowledge informs application of the law in cases related to HIV.

Reducing Risk: Counseling Men Infected with HIV Who Have Sex with Men on Safer Sex Practices with Seroconcordant Partners

The incidence of new HIV infections in the United States continues to be greatest among men who have sex with men (MSM). MSM infected with HIV often seek seroconcordant sexual partners based on intent to limit psychosocial, legal, and health risks they perceive as higher with serodiscordant sexual partners. However, the rationales for limiting sexual relationships exclusively with other MSM infected with HIV may be rooted in misinformation or misperception. Thus, these clients may have a unique sexual health knowledge deficit that nurses, social workers, and other clinicians need to address to help them reduce risk. This article focuses on sexually related health risks that are distinct to MSM infected with HIV seroconcordant partners. Data on the most recent HIV-infection incidence rates in MSM in the United States is provided. Discussion concentrates on the risk these individuals may have in communicating and acquiring sexually transmitted diseases other than HIV, the risk of HIV superinfection, and how sexually transmitted diseases affect persons who are immunocompromised differently than those who are immunocompetent. Finally, recommendations for healthcare professionals who counsel MSM infected with HIV in sexual decision making is provided.

Large cluster outbreaks sustain the HIV epidemic among MSM in Quebec

OBJECTIVE

HIV-1 epidemics among MSM remain unchecked despite advances in treatment and prevention paradigms. This study combined viral phylogenetic and behavioural risk data to better understand underlying factors governing the temporal growth of the HIV epidemic among MSM in Quebec (2002-2015).

METHODS

Phylogenetic analysis of pol sequences was used to deduce HIV-1 transmission dynamics (cluster size, size distribution and growth rate) in first genotypes of treatment-naïve MSM (2002-2015, n = 3901). Low sequence diversity of first genotypes (0-0.44% mixed base calls) was used as an indication of early-stage infection. Behavioural risk data were obtained from the Montreal rapid testing site and primary HIV-1-infection cohorts.

RESULTS

Phylogenetic analyses uncovered high proportion of clustering of new MSM infections. Overall, 27, 45, 48, 53 and 57% of first genotypes within one (singleton, n = 1359), 2-4 (n = 692), 5-9 (n = 367), 10-19 (n = 405) and 20+ (n = 1277) cluster size groups were early infections (<0.44% diversity). Thirty viruses within large 20+ clusters disproportionately fuelled the epidemic, representing 13, 25 and 42% of infections, first genotyped in 2004-2007 (n = 1314), 2008-2011 (n = 1356) and 2012-2015 (n = 1033), respectively. Of note, 35, 21 and 14% of MSM belonging to 20+, 2-19 and one (singleton) cluster groups were under 30 years of age, respectively. Half of persons seen at the rapid testing site (2009-2011, n = 1781) were untested in the prior year. Poor testing propensity was associated with fewer reported partnerships.

CONCLUSION

Addressing the heterogeneity in transmission dynamics among HIV-1-infected MSM populations may help guide testing, treatment and prevention strategies.

On-Demand Preexposure Prophylaxis in Men at High Risk for HIV-1 Infection

BACKGROUND

Antiretroviral preexposure prophylaxis has been shown to reduce the risk of human immunodeficiency virus type 1 (HIV-1) infection in some studies, but conflicting results have been reported among studies, probably due to challenges of adherence to a daily regimen.

METHODS

We conducted a double-blind, randomized trial of antiretroviral therapy for preexposure HIV-1 prophylaxis among men who have unprotected anal sex with men. Participants were randomly assigned to take a combination of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) or placebo before and after sexual activity. All participants received risk-reduction counseling and condoms and were regularly tested for HIV-1 and HIV-2 and other sexually transmitted infections.

RESULTS

Of the 414 participants who underwent randomization, 400 who did not have HIV infection were enrolled (199 in the TDF-FTC group and 201 in the placebo group). All participants were followed for a median of 9.3 months (interquartile range, 4.9 to 20.6). A total of 16 HIV-1 infections occurred during follow-up, 2 in the TDF-FTC group (incidence, 0.91 per 100 person-years) and 14 in the placebo group (incidence, 6.60 per 100 person-years), a relative reduction in the TDF-FTC group of 86% (95% confidence interval, 40 to 98; P=0.002). Participants took a median of 15 pills of TDF-FTC or placebo per month (P=0.57). The rates of serious adverse events were similar in the two study groups. In the TDF-FTC group, as compared with the placebo group, there were higher rates of gastrointestinal adverse events (14% vs. 5%, P=0.002) and renal adverse events (18% vs. 10%, P=0.03).

CONCLUSIONS

The use of TDF-FTC before and after sexual activity provided protection against HIV-1 infection in men who have sex with men. The treatment was associated with increased rates of gastrointestinal and renal adverse events. (Funded by the National Agency of Research on AIDS and Viral Hepatitis [ANRS] and others; ClinicalTrials.gov number, NCT01473472.).

High HIV incidence among men who have sex with men attending a community-based voluntary counselling and testing service in Barcelona, Spain: results from the ITACA cohort

OBJECTIVES

To identify the HIV incidence and its associated factors (AFs) of the ITACA, a community-based cohort of HIV-negative men who have sex with men (MSM) established in Barcelona, Spain from 2008 to 2011.

METHODS

Participants were men aged 18 years or older, having a negative HIV test result at baseline and agreeing to participate. Bio-behavioural data were collected by peers in each visit. HIV incidence rates using person-time measures and 95% CIs were calculated. Cox logistic regression models were used to identify AFs to seroconversion.

RESULTS

Over the period, 3544 participants with at least one follow-up visit or those who had a first visit no longer than a year prior to the date of data censoring were included in the analysis contributing 3567.09 person-year (p-y) and 85 MSM seroconverted for an overall HIV incidence of 2.4 per 100 p-y (95% CI 1.9 to 2.9) ranging from 1.21/100 (2009) to 3.1/100 p-y (2011). Independent AF included: foreign origin, having more than five HIV tests at baseline, reporting in the preceding 6 months the following: condomless anal sex with the last steady partner of unknown serostatus, more than 10 casual partners, condomless anal sex with casual partner, self-reported gonorrhoea and entered in the cohort in 2010 or 2011.

CONCLUSIONS

The ITACA cohort revealed a high and increasing HIV incidence among MSM, especially important among foreign-born men. The findings underscore the need to implement multilevel interventions for MSM taking into account different types of partners, cultural origins and the exposure to other sexually transmitted infections.

Incident risk factors as predictors of HIV seroconversion in the Lisbon cohort of men who have sex with men: first results, 2011-2014

HIV incidence in men who have sex with men (MSM) is increasing in western countries, including Portugal. We aimed to estimate HIV incidence and to assess how individual short-term changes in exposures over time predict seroconversion. We evaluated participants of an open cohort of HIV-negative MSM enrolled after testing at a community-based voluntary HIV counselling and testing centre in Lisbon. At each evaluation a structured questionnaire was completed and HIV status was ascertained using rapid followed by confirmatory testing. Between April 2011 and February 2014, 804 MSM were followed for a total of 893 person-years. Predictors of HIV seroconversion were identified using Poisson generalised linear regression. The overall seroincidence was 2.80/100 person-years (95% confidence interval: 1.89-4.14). Men who seroconverted had a higher mean number of tests per year. Seroconversions were significantly associated with partner disclosure of HIV status during follow-up, newly-adopted unprotected anal intercourse (UAI) with a steady partner and being newly-diagnosed with syphilis during follow-up. Likewise, sexual intercourse with HIV-positive men, having an HIV-positive steady partner at least once during follow-up and persistent UAI with occasional partners were predictors of seroconversion. High HIV incidence in this cohort is likely driven by short-term contextual and behavioural changes during follow-up.

HIV incidence and associated factors in a cohort of men who have sex with men in Nanjing, China

BACKGROUND

Many surveys conducted in recent years reported the increasing trend of HIV infection among men who have sex with men (MSM), but limited data exists on HIV incidence by cohort study in China.

METHODS

A 6-month prospective cohort study was conducted. A total of 397 MSM found HIV seronegative at baseline study were followed-up for 6 months starting from May 2007 and re-evaluated seroconversions of HIV at 6 months. Questionnaire interviews were conducted to collect information about risk behaviors.

RESULTS

Of the 397 MSM who were found seronegative at the baseline study, 286 (72.0%) received the HIV antibody testing at month 6; 7 of them showed HIV seroconversions, yielding an incidence of 5.12 per 100 person-years. Significant predictors of seroconversion (Poisson regression analyses) included duration being MSM >10 years (relative risks [RR] = 3.08, 95% CI: 1.53-6.20), recruiting male sex partner mostly at saunas (RR = 2.35, 95% CI:1.09-5.08), positive syphilis diagnosis made at the baseline study (RR = 2.82, 95% CI: 1.31-6.09), having multiple male sex partners in the last 6 months (RR = 2.54, 95% CI: 1.18-5.49), having at least 1 casual male sex partner in the last 6 months (RR = 2.17, 95% CI: 1.00-4.70), and having unprotected anal sex with a regular male sex partner in the last 6 months (RR = 2.22, 95% CI: 1.10-4.49).

CONCLUSIONS

The incidence of HIV among MSM is very high; many new infections would hence occur in China. Effective interventions are warranted. The risk factors reported in this study give some insights for designing relevant prevention programs.

Future of phylogeny in HIV prevention

The success of the HIV Prevention Trials Network 052 trial has led to revisions in HIV-1 treatment guidelines. Antiretroviral therapy may reduce the risk of HIV-1 transmissions at the population level. The design of successful treatment as prevention interventions will be predicated on a comprehensive understanding of the spatial, temporal, and biological dynamics of heterosexual men who have sex with men and intravenous drug user epidemics. Viral phylogenetics can capture the underlying structure of transmission networks based on the genetic interrelatedness of viral sequences and cluster networks that could not be otherwise identified. This article describes the phylogenetic expansion of the Montreal men who have sex with men epidemic over the last decade. High rates of coclustering of primary infections are associated with 1 infection leading to 13 onward transmissions. Phylogeny substantiates the role of primary and recent stage infection in transmission dynamics, underlying the importance of timely diagnosis and immediate antiretroviral therapy initiation to avert transmission cascades.

Risk patterns preceding diagnosis among newly HIV-diagnosed men who have sex with men in New York City

Men who have sex with men (MSM) are at high risk for contracting and transmitting HIV. They are increasingly encouraged to get tested, but understanding of the interplay between HIV testing and risk behavior is limited. One hundred fifty newly HIV-diagnosed (within past 3 months) MSM were recruited from a community clinic in New York City. Participants completed an interview assessing sexual behavior and substance use during the 3 months pre-diagnosis, current depressive symptoms, and prior HIV testing. HIV-related health characteristics at diagnosis were abstracted from medical records. Analyses examined factors associated with unprotected anal intercourse (UAI) in the 3 months pre-diagnosis, and with a negative HIV test in the 12 months pre-diagnosis. The sample was young (mean age=32.5, SD=8.8), ethnically diverse (62% racial/ethnic minority), low-income (71%≤$30,000/year), and educated (48% college/advanced degree). Most (95%) had a prior negative HIV test, 55% within the last 12 months. Significant risk behavior was reported, with 79% reporting UAI. UAI was associated with recent testing and use of substances during sexual behavior. Recent testing was associated with being employed/a student, having had UAI, and higher CD4 count. Implications for future research addressing perceived HIV risk, HIV testing utilization, and risk behavior are discussed.

Serosorting and strategic positioning during unprotected anal intercourse: are risk reduction strategies being employed by gay and bisexual men in Scotland?

BACKGROUND

Unprotected anal intercourse (UAI) remains the main risk factor for HIV among men who have sex with men (MSM), but risk varies by the sexual position adopted and the risk reduction strategies used. Here, we report on sexual position, and knowledge of partners' HIV status, during UAI to assess whether MSM in Scotland are using sexual risk reduction strategies.

METHODS

Anonymous, self-complete questionnaires and Orasure oral fluid specimens (OraSure Technologies, Inc., Bethlehem, Pennsylvania, USA) were provided by 1277 MSM in commercial gay venues in Glasgow and Edinburgh, Scotland, United Kingdom (59.7% response rate). Overall, 488 MSM (39.7%) reported any UAI in the past 12 months; 318 reported on partner HIV status and sexual position and are included in these analyses.

RESULTS

Being equally either the insertive or receptive partner during UAI was most commonly reported; 23.1% of HIV-negative MSM reported exclusive insertive UAI, whereas no MSM with diagnosed HIV reported exclusive receptive UAI. Five diagnosed HIV-positive MSM reported always knowing their partners' HIV status and only having HIV-positive partners (50.0% of HIV-positive MSM reporting UAI; 11.9% of the diagnosed HIV-positive sample); 160 HIV-negative MSM reported having had an HIV test (and therefore being aware of their HIV-negative status), always knowing their partners' status, and only having HIV-negative partners (52.8% of HIV-negative MSM reporting UAI; 13.7% of the total HIV-negative sample).

CONCLUSIONS

Behavior suggestive of serosorting and strategic positioning (among HIV-negative MSM) was evident in this sample, but inconsistent adoption of these and general versatility in sexual behavior suggest that they have a limited role.

Transmission clustering drives the onward spread of the HIV epidemic among men who have sex with men in Quebec

Phylodynamic analysis and epidemiologic data identified 3 patterns of spread of primary human immunodeficiency virus type 1 infection (PHI) among men who have sex with men (2001-2009): 420 unique PHIs, 102 small clusters (2-4 PHIs per cluster, n = 280), and 46 large clusters (5-31 PHIs per cluster, n = 450). Large clusters disproportionately increased from 25.2% of PHIs in 2005 to 39.1% in 2009 (χ(2) = 33.9, P < .001). Scalar expansion of large clusters over 11 months (interquartile range, 3.5-25.5 months) correlated with cluster membership size (r(2) = 0.174, F = 4.424, P = .047). PHI cohort data revealed variations in social networks and risk behaviors among the 3 groups, suggesting the need for tailored prevention measures.

Risk of window period HIV infection in high infectious risk donors: systematic review and meta-analysis

The OPTN defines high risk donors (HRDs), colloquially known as 'CDC high risk donors', as those thought to carry an increased risk of HIV window period (WP) infection prior to serologic detectability. However, the true risk of such infection remains unknown. To quantify the risk of WP infection in each HRD behavior category, we performed a systematic review and meta-analysis of studies of HIV prevalence and incidence. Of 3476 abstracts reviewed, 27 eligible studies of HIV infection in HRD populations were identified. Pooled HIV incidence estimates were calculated for each category of HRD behavior and used to calculate the risk of WP HIV infection. Risks ranged from 0.09-12.1 per 10 000 donors based on WP for ELISA and 0.04-4.9 based on nucleic acid testing (NAT), with NAT reducing WP risk by over 50% in each category. Injection drug users had the greatest risk of WP infection (4.9 per 10 000 donors by NAT WP), followed by men who have sex with men (4.2:10 000), commercial sex workers (2.7:10 000), incarcerated donors (0.9:10 000), donors exposed to HIV through blood (0.6:10 000), donors engaging in high-risk sex (0.3:10 000) and hemophiliacs (0.035:10 000). These estimates can help inform patient and provider decision making regarding HRDs.

Confidentiality of the medical records of HIV-positive patients in the United Kingdom - a medicolegal and ethical perspective

This article examines the legal and ethical issues that surround the confidentiality of medical records, particularly in relation to patients who are HIV positive. It records some historical background of the HIV epidemic, and considers the relative risks of transmission of HIV from individual to individual. It explains the law as it pertains to confidentiality, and reports the professional guidance in these matters. It then considers how these relate to HIV-positive individuals in particular.

Syphilis and HIV seroconversion among a 12-month prospective cohort of men who have sex with men in Shenyang, China

BACKGROUND

Cross-sectional studies have found a high prevalence of syphilis and HIV infection among men who have sex with men (MSM) in China.

METHODS

A total of 218 HIV-negative MSM participated in this prospective cohort study. Interviewer-administered questionnaires were completed, and blood samples were obtained for HIV and syphilis testing, both upon enrollment and at 12-month follow-up.

RESULTS

Of enrolled participants, 56% (122) were retained for the full 12-month follow-up period. The cohort had an HIV incidence density of 5.4 (95% CI: 2.0-11.3)/100 person-year (PY) and a syphilis incidence density of 38.5(95% CI: 27.7-50.2)/100 PY. Having syphilis (odds ratio [OR]: 11.4, 95% CI: 1.2-104.7) and more than 5 male sexual partners within the past 12 months (OR: 6.5, 95% CI: 1.1-39.8) were independent risk factors for HIV seroconversion (each P < 0.05). Being married (OR: 3.5, 95% CI: 1.4-8.2) and having more than 5 male sexual partners within the past 12 months (OR: 4.7, 95% CI: 2.0-6.2) were risk factors for syphilis seroconversion, while age > or =30 (OR 2.1, 95% CI 0.7-9.5) and having recently engaged in unprotected receptive anal sex (OR: 2.4, 95% CI: 0.7-13.1) were marginally associated with syphilis seroconversion.

CONCLUSION

The high incidence rates of HIV and syphilis in the Shenyang MSM community are significant cause for concern. The seroconversion rate for syphilis, in particular, indicates the high prevalence of high-risk sexual behaviors and the potential for increased HIV transmission. Appropriate interventions that address MSM-specific issues, including stigma, pressures from traditional society, and bisexual behavior, need to be tailored to inform and empower MSM in order to prevent HIV and syphilis in this community.

Running in place: implications of HIV incidence estimates among urban men who have sex with men in the United States and other industrialized countries

Attempts to document changing HIV incidence rates among MSM are compromised by issues of generalizability and statistical power. To address these issues, this paper reports annualized mean HIV incidence rates from the entire published incidence literature on MSM from Europe, North America and Australia for the period 1995-2005. Publications that met the entry criteria were coded for region of the world, sampling method and year of study. From these reports, we calculated a mean incidence rate with confidence intervals for these variables. Although no differences in mean incidence rates were found for MSM from 1995 to 2005, HIV incidence rates are lower in Australia than either North America or Europe. We calculated a mean incidence rate of 2.39% for MSM in the United States, which if sustained within a cohort of MSM, would yield HIV prevalence rate of approximately 40% at age 40. These extrapolations overlap published HIV prevalence rates for MSM younger than age 40 in the United States. HIV incidence rates in the 2-3% range will adversely affect the health of gay male communities for decades to come. This analysis suggests that greater attention should be devoted to the question of how best to design prevention interventions that will lower HIV incidence rates among gay men.

Systematic review of orogenital HIV-1 transmission probabilities

Background The objective was to assess the risk of HIV transmission from orogenital intercourse (OI).

Methods Systematic review of the literature on HIV-1 infectiousness through OI conducted according to MOOSE guidelines for reviews of observational studies. The PubMed database and bibliographies of relevant articles were searched to July 2007.

Results Of the titles, 56 214 were searched from which 10 potentially appropriate studies were identified; two additional studies were identified through bibliographies and one through discussion with experts. There were 10 included studies, providing estimates of transmission probabilities per-partner (n = 5), incidence per-partner (n = 3), per-study participant (n = 3, following initially seronegative individuals whose partners are of unknown serostatus) and per-act (n = 3). Only four of 10 studies reported non-zero estimates: two per-partner estimates (20%, 95% CI: 6–51, n = 10 and a model-based estimate, 1%, range 0.85–2.3%), one per-study participant estimate (0.37%, 95% CI: 0.10–1.34%) and one per-act estimate (0.04%, 95% CI: 0.01–0.17%). Upper bounds for the 95% CI for zero estimates tended to be relatively large due to the small study sample sizes: 9.0, 12.1 and 2.8% for per-partner; 4.7, 9.6 and 1.8 per 100 person-years for incidence per-partner; 4.4% per-study participant and 0.45 and 0.02% for per-act. Given the small number of studies, a meta-analysis was not considered appropriate.

Conclusions There are currently insufficient data to estimate precisely the risk from OI exposure. The low risk of transmission evident from identified studies means that more and larger studies would be required to provide sufficient evidence to derive more precise estimates.