References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
HIV is transmitted through specific body fluids — blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids and breast milk. It cannot be transmitted through saliva, sweat, tears, urine or casual contact. And crucially, when someone with HIV is on effective treatment with an undetectable viral load, they cannot pass HIV on sexually. This is U=U — Undetectable = Untransmittable.
Here’s the full picture of how HIV is and isn’t transmitted.
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How HIV Is Transmitted
| Route | Risk Level |
|---|---|
| Condomless anal sex (receptive) | Highest per-act risk |
| Condomless anal sex (insertive) | Moderate |
| Condomless vaginal sex | Lower than anal, but real |
| Sharing injecting equipment | High |
| Mother to child (pregnancy, birth, breastfeeding) | Without treatment: 15-45%. With treatment: below 1% |
| Needlestick injury | Low (about 0.23%) |
| Oral sex | Very low — not reliably quantifiable |
How HIV Is NOT Transmitted
- Kissing, hugging, shaking hands
- Sharing food, drinks, cutlery
- Sharing toilets, bathrooms, swimming pools
- Coughing, sneezing
- Insect bites
- Saliva, sweat, tears, urine
- Being in the same room as someone with HIV
U=U: The Game-Changer
Undetectable = Untransmittable means that when a person with HIV is on effective treatment and has a sustained undetectable viral load, there is zero risk of sexual transmission. This is supported by landmark studies:
- PARTNER 1 and 2 — over 135,000 acts of condomless sex, zero transmissions
- HPTN 052 — 96% reduction in transmission with early treatment; zero while undetectable
- Opposites Attract — 17,000 acts, zero transmissions
U=U is endorsed by the NHS, BHIVA, WHO, UNAIDS and over 1,000 organisations worldwide.
What Reduces Transmission Risk
- ART with undetectable viral load (U=U) — eliminates sexual transmission
- PrEP — over 99% effective for the HIV-negative partner
- Condoms — highly effective barrier protection
- PEP — emergency prevention within 72 hours of exposure
- Clean injecting equipment
- Treating other STIs — reduces biological vulnerability
Read more: U=U for partners | Estimating risk | What is HIV?
Frequently Asked Questions
Can I get HIV from kissing?
No. HIV is not transmitted through saliva. Deep kissing carries no HIV risk.
Is U=U really zero risk?
Yes. The combined evidence from major studies involving over 100,000 acts of condomless sex found zero transmissions from partners with undetectable viral loads.
Can HIV be transmitted through oral sex?
The risk is very low — so low it hasn’t been reliably quantified. It’s considered negligible in practical terms.
Related reading
- Injectable HIV Treatment: Everything You Need to Know
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
- Can You Catch an STI From a Toilet Seat?
- Can You Get Chlamydia From Kissing?
- Can You Get Herpes From a Toilet Seat?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
