Undetectable = Untransmittable (U=U) is proven by several studies. In 2016, the PARTNER study from Europe found that the chance of HIV transmission where one partner had a UVL is negligible. In fact, there were zero partner-transmissions recorded in the study despite approximately 22,000 acts of condomless sex and not using PrEP by MSM couples. Additionally, PARTNER2 – the extension study of PARTNER that aimed to gather data pertaining to mixed-HIV-status gay male couples – found that after an additional 54,000 acts of condomless sex there were zero transmissions.
Another study led by the Kirby Institute, the Opposites Attract study, which focused solely on gay and other men who have sex with men from Australia, Brazil and Thailand, confirmed that HIV positive men who are on treatment and have an undetectable viral load do not transmit the virus to their partners.
Thus, receiving proper treatment as early as possible can effectively manage the body condition and prevent transmission of HIV.