What is the risk of Human Immunodeficiency Virus (HIV) transmission through sexual contact?

From the Guidelines

The risk of HIV transmission through sexual contact is estimated to be 0.1%–0.2% for vaginal intercourse and 0.5%–3% for receptive rectal intercourse, with the per-act risk for HIV transmission from oral sex being substantially lower 1. When considering the risk of HIV transmission, several factors come into play, including the type of sexual act, the viral load of the HIV-positive partner, and the presence of other sexually transmitted diseases.

• The risk of HIV transmission is higher for receptive anal intercourse, with a range of 0.5%–3% per act 1.
• For vaginal intercourse, the risk is lower, ranging from 0.1%–0.2% per act 1.
• Oral sex poses a significantly lower risk of HIV transmission, although the exact percentage is not specified in the guidelines 1. It's essential to note that these risks can be significantly reduced with the use of post-exposure prophylaxis (PEP) and pre-exposure prophylaxis (PrEP), as well as consistent and correct condom use.
• PEP, when initiated as soon as possible after exposure, can reduce the risk of acquiring HIV by 81% 1.
• The guidelines recommend assessing the risk of HIV transmission and offering nPEP to survivors of sexual assault, taking into account factors such as the likelihood of the assailant having HIV, exposure characteristics, and the time elapsed after the event 1.

From the Research

HIV Sexual Transmission Risk

• The risk of HIV transmission through sexual contact is influenced by various factors, including the choice of partner, sex act, and condom use 2.
• Studies have shown that the per-act relative risk for HIV infection can be significantly reduced by choosing a partner who has tested negative for HIV, using condoms, and opting for lower-risk sex acts such as insertive fellatio instead of insertive anal sex 2.
• The use of pre-exposure prophylaxis (PrEP) with antiretroviral agents such as tenofovir disoproxil fumarate (TDF) and emtricitabine has been shown to be highly effective in preventing HIV transmission, with an efficacy of over 90% when used daily and adhered to properly 3, 4.
• However, the risk of HIV transmission is not entirely eliminated, even with the use of PrEP or antiretroviral therapy (ART), especially if the viral load is not well-controlled 5.
• A systematic review of studies on the risk of sexual transmission of HIV in individuals with low-level HIV viraemia found that there is almost zero risk of transmission when the viral load is less than 1000 copies per mL 5.

Factors Affecting HIV Transmission Risk

• Choice of partner: Choosing a partner who has tested negative for HIV can reduce the relative risk of HIV infection by 47-fold 2.
• Condom use: Using condoms can reduce the relative risk of HIV infection by 20-fold 2.
• Sex act: Opting for lower-risk sex acts such as insertive fellatio instead of insertive anal sex can reduce the relative risk of HIV infection by 13-fold 2.
• Viral load: Having a well-controlled viral load, especially less than 1000 copies per mL, can significantly reduce the risk of HIV transmission 5.

Prevention Strategies

• Pre-exposure prophylaxis (PrEP) with antiretroviral agents such as TDF and emtricitabine 3, 4.
• Post-exposure prophylaxis (PEP) 6.
• Antiretroviral therapy (ART) to suppress viral load 5.
• Patient education and counseling on risk reduction strategies 6.
• Use of condoms and other barrier methods 2.