U = U means undetectable equals untransmittable. This slogan refers to the fact that there is effectively no risk of sexually transmitting HIV when the virus is reduced to undetectable levels.
An undetectable viral load for people living with HIV means they will not transmit HIV to their partners. Active engagement in treatment as prevention is a key to maintaining an undetectable viral load and preventing HIV transmission. ‘Treatment as Prevention’ (TasP) is defined as any HIV prevention method that uses antiretroviral therapy (ART) to decrease the risk of HIV transmission to a sexual or needle-sharing partner. ART reduces HIV in blood, semen, vaginal fluid, and rectal fluid to very low levels, and as a result, lowers HIV transmission. ART can even lower viral load to undetectable levels.
Evidence from real-world studies including PARTNER and Opposites Attract shows the affect TasP and ART have on preventing HIV transmission in the PARTNER study that there were ZERO transmissions out of 58,000 condomless sex acts between people with undetectable HIV viral loads and their HIV-negative partners. In the Opposites Attract study, there were no transmissions out of 17,000 condomless sex acts between men. Since the advent of combination therapy, there have been no confirmed reports of anyone with an undetectable viral load sexually transmitting HIV.
An important aspect to TasP is regular viral load testing. Testing is recommended about 2-4 times a year for people who have a stable undetectable viral load. More frequent testing may be necessary and it is recommended that people speak with their doctors about appropriate care, treatment, and testing.
Evidence shows that with regular testing and continued treatment, people living with undetectable HIV viral loads may let go of fears about transmitting HIV to their partners. Instead, we can all focus on the fact undetectable does equal untransmitable.
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