Sexual Contact:

• Vaginal/Anal Sex: 1–3 per 1,000 exposures (higher for receptive anal sex).
• Oral Sex: <1 per 1,000 exposures (low risk due to lower viral load in saliva).
• Rationale: Transmission depends on viral load, presence of STIs, and mucosal damage.

• Blood/Needle Exposure:
  • Needle Stick: ~0.3% per exposure (higher for larger volumes).
  • Blood Transfusion: Near 0% (due to screening).

• Mother-to-Child:
  • Perinatal: 15–30% without ART; <1% with ART + PMTCT.
  • Breastfeeding: 5–20% without ART; ~1% with ART.

• Other Routes:
  • Kissing: No documented cases (saliva has low viral load, no blood exchange).
  • Casual Contact (Hugging, Sharing Utensils): No risk (virus unstable outside body).

• Key Factors:
  • Viral load (higher = increased risk).
  • Presence of STIs (e.g., HSV, syphilis) disrupts mucosal barriers.
  • ART reduces transmission risk by ~96% (UNAIDS, 2023).

Sources:

• WHO (2023), CDC (2022), UNAIDS (2023) guidelines.