What is U=U?
What Does “Undetectable = Untransmittable” Mean?
“Undetectable” means that a lab test cannot detect the virus in the blood of a person living with HIV. Although extremely small amounts of HIV are still present, these are not considered infectious. Someone who takes HIV treatment and is “undetectable” for six or more continuous months does not transmit the virus through sex.
Undetectable also means the virus is being well controlled by HIV meds. If a person with undetectable HIV stops their medications, the virus returns to a detectable level, which then increases the risk of transmission.
The lingo
U=U is short for “undetectable = untransmittable.” Treatment as prevention, or “TasP.” Generally, these terms mean the same thing: If a person living with HIV stays undetectable for six months or more while on treatment, they cannot transmit HIV through sex.
The scientific evidence
Three global studies showed no HIV transmissions within mixed-status couples when the partner with HIV was undetectable for six or more months. This included more than 126,000 acts of reported condomless sex among mixed-status heterosexual and gay male couples. (The studies were HPTN 052, PARTNER, and Opposites Attract.) To date worldwide, there are no verified reports of someone getting HIV from a partner who is undetectable.
Related Resources
NYC Health: Undetectable Equals Untransmittable (U=U)
This page from the New York City Department of Health provides information on HIV, its treatment, and testing services.
HIV Treatment, the Viral Reservoir, and HIV DNA
This page from the National Institutes of Health describes antiretroviral therapy (ART) and its role in treating and preventing HIV infection.
Men Living with HIV
This page from the University of San Francisco provides information to empower you to make informed decisions about sex, relationships, and family planning.
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