Risk of HIV Transmission via Sexual Contact:
- Vaginal Intercourse:
- Estimated risk per act: ~0.08% (range: 0.04–0.13%) for receptive partner, ~0.04% for insertive partner.
- Rationale: Higher risk for receptive partner due to greater mucosal exposure.
- Anal Intercourse:
- Estimated risk per act: ~1.42% (range: 0.62–2.22%) for receptive partner, ~0.06% for insertive partner.
- Rationale: Higher risk due to delicate rectal mucosa and potential for microtears.
- Oral Sex:
- Estimated risk per act: ~0.04% (range: 0.00–0.04%) for receptive partner, negligible for insertive partner.
- Rationale: Lower risk due to fewer mucosal breaks and lower viral loads in saliva.
- Modifying Factors:
- Higher Risk: Genital ulcers (e.g., HSV, syphilis), STIs, bleeding, or trauma.
- Lower Risk: Effective ART (viral suppression), PrEP, PEP, or condom use.
- Key Mechanisms:
- HIV is present in genital secretions (semen, vaginal fluid) and blood.
- Transmission occurs via mucosal contact with infected fluids, facilitated by breaks in mucosal integrity.
- Guidelines:
- CDC: Condoms reduce risk by ~70–80% when used consistently and correctly.
- WHO: ART for HIV+ individuals reduces transmission risk to near zero when viral load is undetectable.
- Research Evidence:
- HPTN 052 trial: ART reduced HIV transmission in discordant couples by 96%.
- PARTNER study: No linked transmissions in couples where HIV+ partner had undetectable viral load.