Quick Answer
U=U (Undetectable = Untransmittable) is the scientific consensus that people with HIV who maintain an undetectable viral load through consistent ART cannot transmit HIV sexually. This is supported by multiple large studies with zero linked transmissions.
- PARTNER studies: 77,000+ condomless sex acts, zero transmissions
- U=U applies to all sexual acts: anal, vaginal, oral
- Requires: consistent ART, viral load <200 copies/mL
- U=U does NOT apply to pregnancy or breastfeeding
Context Most Pages Skip
U=U transformed the HIV landscape. It eliminates the sexual transmission risk from people on effective treatment.
The Evidence
The PARTNER and HPTN 052 studies tracked thousands of serodifferent couples over years. Zero linked HIV transmissions occurred when the partner with HIV was undetectable. This is one of the best-proven facts in modern medicine.
⚕️ This page is educational and does not replace advice from a licensed clinician. If you may have been exposed to an STI, get tested — most infections are manageable, and many are fully curable.
Sources & Further Reading
- CDC — Sexually Transmitted Infections
- CDC STI Treatment Guidelines
- WHO — Sexually transmitted infections fact sheet
- MedlinePlus — Sexually Transmitted Diseases
Figures reflect CDC surveillance and WHO estimates; they are population statistics, not personal risk predictions.