HIV transmission risk through anal intercourse: systematic review, meta-analysis and implications for HIV prevention

Abstract

Background The human immunodeficiency virus (HIV) infectiousness of anal intercourse (AI) has not been systematically reviewed, despite its role driving HIV epidemics among men who have sex with men (MSM) and its potential contribution to heterosexual spread. We assessed the per-act and per-partner HIV transmission risk from AI exposure for heterosexuals and MSM and its implications for HIV prevention.Methods Systematic review and meta-analysis of the literature on HIV-1 infectiousness through AI was conducted. PubMed was searched to September 2008. A binomial model explored the individual risk of HIV infection with and without highly active antiretroviral therapy (HAART).Results A total of 62 643 titles were searched; four publications reporting per-act and 12 reporting per-partner transmission estimates were included. Overall, random effects model summary estimates were 1.4% [95% confidence interval (CI) 0.2–2.5)] and 40.4% (95% CI 6.0–74.9) for per-act and per-partner unprotected receptive AI (URAI), respectively. There was no significant difference between per-act risks of URAI for heterosexuals and MSM. Per-partner unprotected insertive AI (UIAI) and combined URAI–UIAI risk were 21.7% (95% CI 0.2–43.3) and 39.9% (95% CI 22.5–57.4), respectively, with no available per-act estimates. Per-partner combined URAI–UIAI summary estimates, which adjusted for additional exposures other than AI with a ‘main’ partner [7.9% (95% CI 1.2–14.5)], were lower than crude (unadjusted) estimates [48.1% (95% CI 35.3–60.8)]. Our modelling demonstrated that it would require unreasonably low numbers of AI HIV exposures per partnership to reconcile the summary per-act and per-partner estimates, suggesting considerable variability in AI infectiousness between and within partnerships over time. AI may substantially increase HIV transmission risk even if the infected partner is receiving HAART; however, predictions are highly sensitive to infectiousness assumptions based on viral load.Conclusions Unprotected AI is a high-risk practice for HIV transmission, probably with substantial variation in infectiousness. The significant heterogeneity between infectiousness estimates means that pooled AI HIV transmission probabilities should be used with caution. Recent reported rises in AI among heterosexuals suggest a greater understanding of the role AI plays in heterosexual sex lives may be increasingly important for HIV prevention.

Vulnerability in the context of HIV and syphilis infection in a population of men who have sex with men (MSM) in Salvador, Bahia State, Brazil

“…The latter was more common in this study when compared to patterns in other countries 1 : two RDS studies showed lower percentages 25,41 than in Salvador. However, regarding casual partners, other RDS showed similar percentages to those found in this research 27,30 , indicating high exposure of MSM in Salvador, since the probability of HIV infection can reach 40.4% per sexual partner in unprotected receptive anal sex 37 .…”

“…A factor related to the sexual practices of MSM and which was associated with HIV infection and other STI is the high number of partners, which can increase their exposure to HIV infection, especially with inconsistent condom use in receptive anal sex, which can occur due to alcohol use, psychoactive substances before and during sex, or as a result of stigma and discrimination 37,38 . Some RDS studies have found fewer sexual partners than in this study 24,28,39,40 , but our findings are close to other results of RDS studies with MSM 6,25,27,30 .…”

Fatores associados à prevalência do vírus da imunodeficiência humana em população privada de liberdade

“…Sexual exposure is still the major transmission route for HIV, including prison inmates in Brazil, who are commonly ignored by preventive campaigns (19) . Studies have confirmed that receptive anal sexual intercourse has an increased risk of 1.4%, 18 times more in comparison with other practices (20)(21) . This practice is associated with homosexual relationships, but is also not rare in heterosexual relationships.…”

How partnership type and HIV seroconcordance affect HIV transmission risk in regular sexual partnerships: a cross-sectional survey of Australian gay and bisexual men

“…3 Approximately one-third of infections among newly diagnosed men in Australia are estimated to be from regular partners, [4][5][6] whereas modelling from the US estimates that 68% of infections in GBM are from 'main' partners. 7 Intimacy and familiarity with partners have been associated with increased CLAI among GBM, [8][9][10][11] and HIV prevention and research have described ongoing sexual relationships as potentially high risk for HIV transmission.…”