Are people with HIV contagious?
HIV-positive persons who regularly take antiretroviral therapy (ART) significantly reduce the risk of transmission of infection to HIV-negative sexual partners. People with HIV who achieve viral suppression and maintain it at an immeasurable level have no risk of sexually transmitting HIV.
What exactly does the abbreviation U=U mean?
U=U is an abbreviation of “undetectable = untransmittable”.
The first U refers to immeasurable viral load, when the number of viral copies (HIV particles) is so small that it cannot be measured by a quantitative PCR test.
The second U refers to non-contagiousness, or the impossibility of transmitting HIV sexually.
How reliable is the information that people who have immeasurable viral load are non-infectious?
The information is 100% reliable for HIV+ people who regularly take ART, achieve and maintain viral suppression at an immeasurable level (PCR=0). The risk of transmission is higher in people who do not achieve and maintain viral suppression, do not take ART regularly or stop treatment altogether.
How do we know that U=U?
Four key studies provide evidence of prevention of sexual transmission of HIV due to optimal use of ART: HPTN052 (2016), PARTNER (2016), Opposites Attract (2018), PARTER2 (2018). In these studies, there was zero transmission of HIV infection among serodisparate couples (HIV positive and HIV negative) who did not use condoms during intercourse. HIV-positive persons in the studies used ART therapy with regular viral load checks.