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'Undetectable = Untransmittable' (U=U) is a campaign explaining how the sexual transmission of HIV can be stopped.

When a person is living with HIV and is on effective treatment, it lowers the level of HIV (the viral load) in the blood. When the levels are low (below 200 copies/ml of blood measured) it is referred to as an undetectable viral load. This is also medically known as virally suppressed. At this stage, HIV cannot be passed on sexually.

This scientific evidence was gathered from several studies. The studies included thousands of heterosexual and gay couples in which one partner had HIV and the other did not. Over the course of the studies, they found that there was not a single HIV transmission from an HIV-positive partner who had an undetectable viral load.

When a person is undetectable, condoms are not required to prevent HIV transmission, but being undetectable does not protect against other sexually transmitted infections. So condoms should still be used. 

This understanding transforms the way that HIV is considered with enormous implications for what it now means to live with HIV and the best ways to prevent it.   The preventative impact of effective HIV treatment underlines the importance of expanding access to treatment and of improving treatment uptake and adherence for all people living with HIV worldwide. 

U=U applies to transmission through sex only and cannot be extrapolated to other methods of HIV transmission like breastfeeding or needle sharing.

This is part of a series of monthly posts by:

Dr Donia Gamoudi.

Genitourinary (GU) Medicine doctor 


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