The risk ofhuman immunodeficiency virus(HIV), a virus that can be a sexually transmitted infection (STI), is quite high duringunprotected anal sex(penetrating the rectum).
The anal sex risk is greater than vaginal sex, and greater for a receptive (bottom) partner when the penis is placed in the anus.
This article discusses the increased risk of anal sex for a receptive partner (though the risk exists for a “top” partner too). It presents a number of techniques for reducing this elevated risk of HIV.
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Reasons for Increased Risk
The well-documented reasons for the increased risk that attaches to anal sex, and specifically the bottom partner, include:
Virus in the insertive (“top”) partner’s semen and pre-seminal fluid increases the risk of the receptive partner’s infection with the rise in the HIVviral load(the amount of detectable virus). Some studies suggest route of HIV acquisition and sexual role can influence set point viral loads.
3 Surprising Ways That STIs Increase HIV Risk
HIV Risk Per-Act and Per-Partner
The per-act risk of HIV transmission is based on each sex act. Receptive anal sex presents a much greater risk than other sexual encounters includingoral sex, and each act (of any type) adds up over time.
The Centers for Disease Control and Prevention (CDC) offers data on the per-act risk of HIV that varies across different types of sexual encounter. These risks include:
Theper-partner riskis another wayto evaluate HIV transmission. When HIV infections first began to emerge, and HIV testing was new, researchers learned that the single greatest factor in risk was the number of sex partners with whom one had unprotected receptive anal sex.That risk ranged from 29% with no recent partners to 85% with three or more partners.
Studies on per-partner HIV risk consider a number of variables, including the sex role, whether one or both partners is HIV-positive, the viral loads involved, and access to treatment among them.
Condom Use and Per-Partner Risk
Reducing Risk with Condoms
As with any other mode of HIV transmission, prevention requires a combination of strategies to more effectively:
This is achieved with consistent condom use for protected sex. There are different ways to measure how effective condom use can be in protecting against HIV transmission, exposure per act and per partner among them. Studies have consistently found condom use to be an effective measure.
Condoms also can be used alongside other measures. It remains important, even when people have reduced the HIV transmission risk through medication. The CDC reports only 59.8% of Americans with HIV are able to achieve an undetectable viral load in the infected partner.
To this end, the consistent use of condoms can prevent 7 out of 10 transmissions through anal sex, according to the CDC.
Condoms provide another layer of protection when used with other safer sex practices. Evenantiretroviral therapy (ART)drugs and treatment as prevention (TasP) are not effective unless complete viral suppression is achieved. That leaves the uninfected partner at risk.
How Condoms Prevent HIV
Medications That Prevent Transmission
One study of 1,770 same-sex and heterosexual mixed-status couples found not a single case of HIV transmission, despite engaging in condomless anal or vaginal sex, when antiretroviral therapy (ART) is used.
There are now more than 40 ART drugs available, with different types of drugs in six classes of medication. Some drugs are available as daily combination medications. These ART drugs include:
Post-Exposure Prophylaxis (PEP)If you believe you may have been exposed to HIV, either through a condom burst or condomless anal sex, there are medications that can reduce your risk of infection, referred to as post-exposure prophylaxis (PEP). PEP consists of a 28-day course of antiretroviral drugs, which must be taken completely and without interruption.In order to minimize the risk of infection, PEP must be started as soon as possible, ideally within one to 36 hours of exposure.
Post-Exposure Prophylaxis (PEP)
If you believe you may have been exposed to HIV, either through a condom burst or condomless anal sex, there are medications that can reduce your risk of infection, referred to as post-exposure prophylaxis (PEP). PEP consists of a 28-day course of antiretroviral drugs, which must be taken completely and without interruption.In order to minimize the risk of infection, PEP must be started as soon as possible, ideally within one to 36 hours of exposure.
List of Approved HIV Antiretroviral Drugs
Summary
Medications are also an important therapy. With ART drugs, an infected partner’s viral load can be reduced or achieve undetectable levels, limiting the risk to the uninfected partner. PrEP can help to keep an uninfected partner healthy, while PEP may be able to prevent HIV infection after an exposure if it’s started soon enough.
Be sure to discuss HIV prevention and anal sex transmission risks with your healthcare provider, who can assist with any prevention strategies, diagnosis, or treatment that may be needed.
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.How HIV spreads.Bosinger S, Ackerley CG, Murray PM, Amara RR, Amancha PK, Arthur RA,et al.HIV, asymptomatic STI, and the rectal mucosal immune environment among young men who have sex with men.PLoS Pathog. 2023 May 30;19(5):e1011219. doi:10.1371/journal.ppat.1011219.Stansfield SE, Mittler JE, Gottlieb GS, Murphy JT, Hamilton DT, Detels R, et al.Sexual role and HIV-1 set point viral load among men who have sex with men.Epidemics. 2019 Mar;26:68-76. doi:10.1016/j.epidem.2018.08.006.Prodger JL, Galiwango RM, Tobian AAR, Park D, Liu CM, Kaul R.How Does Voluntary Medical Male Circumcision Reduce HIV Risk?Curr HIV/AIDS Rep.2022 Dec;19(6):484-490. doi:10.1007/s11904-022-00634-w.Centers for Disease Control and Prevention.HIV risk behaviors.Johnson WD, O’Leary A, Flores SA.Per-partner condom effectiveness against HIV for men who have sex with men.AIDS. 2018 Jul 17;32(11):1499-1505. doi:10.1097/QAD.0000000000001832.Centers for Disease Control and Prevention.Understanding the HIV Care Continuum.Centers for Disease Control and Prevention.Anal sex and HIV risk.Rodger A, Cambiano V, Bruun T, et al.Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.Lancet.2019;393(10189):2428-2438. doi:10.1016/S0140-6736(19)30418-0HIVinfo.NIH.gov.FDA-approved HIV medications.Food and Drug Administration.FDA approves first injectable treatment for HIV pre-exposure prevention.Additional ReadingSupervie V, Viard JP, Costagliola D, Breban R.Heterosexual risk of HIV transmission per sexual act under combined antiretroviral therapy: systematic review and Bayesian modelling.Clinical Infectious Diseases.2014;59(1):115-22. doi:10.1093/cid/ciu223
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.How HIV spreads.Bosinger S, Ackerley CG, Murray PM, Amara RR, Amancha PK, Arthur RA,et al.HIV, asymptomatic STI, and the rectal mucosal immune environment among young men who have sex with men.PLoS Pathog. 2023 May 30;19(5):e1011219. doi:10.1371/journal.ppat.1011219.Stansfield SE, Mittler JE, Gottlieb GS, Murphy JT, Hamilton DT, Detels R, et al.Sexual role and HIV-1 set point viral load among men who have sex with men.Epidemics. 2019 Mar;26:68-76. doi:10.1016/j.epidem.2018.08.006.Prodger JL, Galiwango RM, Tobian AAR, Park D, Liu CM, Kaul R.How Does Voluntary Medical Male Circumcision Reduce HIV Risk?Curr HIV/AIDS Rep.2022 Dec;19(6):484-490. doi:10.1007/s11904-022-00634-w.Centers for Disease Control and Prevention.HIV risk behaviors.Johnson WD, O’Leary A, Flores SA.Per-partner condom effectiveness against HIV for men who have sex with men.AIDS. 2018 Jul 17;32(11):1499-1505. doi:10.1097/QAD.0000000000001832.Centers for Disease Control and Prevention.Understanding the HIV Care Continuum.Centers for Disease Control and Prevention.Anal sex and HIV risk.Rodger A, Cambiano V, Bruun T, et al.Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.Lancet.2019;393(10189):2428-2438. doi:10.1016/S0140-6736(19)30418-0HIVinfo.NIH.gov.FDA-approved HIV medications.Food and Drug Administration.FDA approves first injectable treatment for HIV pre-exposure prevention.Additional ReadingSupervie V, Viard JP, Costagliola D, Breban R.Heterosexual risk of HIV transmission per sexual act under combined antiretroviral therapy: systematic review and Bayesian modelling.Clinical Infectious Diseases.2014;59(1):115-22. doi:10.1093/cid/ciu223
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Centers for Disease Control and Prevention.How HIV spreads.Bosinger S, Ackerley CG, Murray PM, Amara RR, Amancha PK, Arthur RA,et al.HIV, asymptomatic STI, and the rectal mucosal immune environment among young men who have sex with men.PLoS Pathog. 2023 May 30;19(5):e1011219. doi:10.1371/journal.ppat.1011219.Stansfield SE, Mittler JE, Gottlieb GS, Murphy JT, Hamilton DT, Detels R, et al.Sexual role and HIV-1 set point viral load among men who have sex with men.Epidemics. 2019 Mar;26:68-76. doi:10.1016/j.epidem.2018.08.006.Prodger JL, Galiwango RM, Tobian AAR, Park D, Liu CM, Kaul R.How Does Voluntary Medical Male Circumcision Reduce HIV Risk?Curr HIV/AIDS Rep.2022 Dec;19(6):484-490. doi:10.1007/s11904-022-00634-w.Centers for Disease Control and Prevention.HIV risk behaviors.Johnson WD, O’Leary A, Flores SA.Per-partner condom effectiveness against HIV for men who have sex with men.AIDS. 2018 Jul 17;32(11):1499-1505. doi:10.1097/QAD.0000000000001832.Centers for Disease Control and Prevention.Understanding the HIV Care Continuum.Centers for Disease Control and Prevention.Anal sex and HIV risk.Rodger A, Cambiano V, Bruun T, et al.Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.Lancet.2019;393(10189):2428-2438. doi:10.1016/S0140-6736(19)30418-0HIVinfo.NIH.gov.FDA-approved HIV medications.Food and Drug Administration.FDA approves first injectable treatment for HIV pre-exposure prevention.
Centers for Disease Control and Prevention.How HIV spreads.
Bosinger S, Ackerley CG, Murray PM, Amara RR, Amancha PK, Arthur RA,et al.HIV, asymptomatic STI, and the rectal mucosal immune environment among young men who have sex with men.PLoS Pathog. 2023 May 30;19(5):e1011219. doi:10.1371/journal.ppat.1011219.
Stansfield SE, Mittler JE, Gottlieb GS, Murphy JT, Hamilton DT, Detels R, et al.Sexual role and HIV-1 set point viral load among men who have sex with men.Epidemics. 2019 Mar;26:68-76. doi:10.1016/j.epidem.2018.08.006.
Prodger JL, Galiwango RM, Tobian AAR, Park D, Liu CM, Kaul R.How Does Voluntary Medical Male Circumcision Reduce HIV Risk?Curr HIV/AIDS Rep.2022 Dec;19(6):484-490. doi:10.1007/s11904-022-00634-w.
Centers for Disease Control and Prevention.HIV risk behaviors.
Johnson WD, O’Leary A, Flores SA.Per-partner condom effectiveness against HIV for men who have sex with men.AIDS. 2018 Jul 17;32(11):1499-1505. doi:10.1097/QAD.0000000000001832.
Centers for Disease Control and Prevention.Understanding the HIV Care Continuum.
Centers for Disease Control and Prevention.Anal sex and HIV risk.
Rodger A, Cambiano V, Bruun T, et al.Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study.Lancet.2019;393(10189):2428-2438. doi:10.1016/S0140-6736(19)30418-0
HIVinfo.NIH.gov.FDA-approved HIV medications.
Food and Drug Administration.FDA approves first injectable treatment for HIV pre-exposure prevention.
Supervie V, Viard JP, Costagliola D, Breban R.Heterosexual risk of HIV transmission per sexual act under combined antiretroviral therapy: systematic review and Bayesian modelling.Clinical Infectious Diseases.2014;59(1):115-22. doi:10.1093/cid/ciu223
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