U=U or ‘Undetectable equals Untransmissable’ means that people living with HIV who achieve and maintain an undetectable viral load (the amount of HIV in the blood) through HIV treatment cannot sexually transmit HIV to others.
Studies have shown that when a person living with HIV has a viral load of less than 200 copies of HIV per milliliter of blood, they cannot pass HIV to sexual partners. Some clinics and health authorities define ‘undetectable’ differently, with a lower number of copies per milliliter. For more information please visit this fact sheet.
HIV specialists will often want to test different people’s viral loads with different frequency, depending on other health factors. In Ontario, it is common for people’s viral load to be tested every 3 months initially, with less frequent testing needed as a person’s viral load stabilizes over time. People living with HIV should follow the directions of their specialist, who will determine how frequently their viral load should be tested.
Maintaining an undetectable viral status leads to the best health outcomes for people living with HIV. Achieving an undetectable viral load will help you to stay healthy, and also prevents the transmission of HIV to sexual partners.
Regular viral tests can determine if your HIV load is undetectable, and are a part of ongoing HIV care. People living with HIV can generally assume that they are undetectable if their viral load has been stable for over 6 months.
Conclusive evidence from numerous clinical trials such as HPTN 052 and PARTNER showed that not a single HIV transmission between serodiscordant sex partners (one partner is HIV positive and the other HIV negative) when the HIV positive partner is on treatment and has an undetectable viral load.
Yes. The PARTNER study concluded that there is zero HIV transmission regardless of type of sex. U=U is applicable to vaginal, oral, and anal sex.
HIV treatment does not prevent other sexually transmitted infections. Condoms are the most effective way to prevent the transmission of common STI’s such as chlamydia, gonorrhoea or syphilis. For some STIs, vaccines are available to prevent infection, including hepatitis B and human papillomavirus (HPV).
Missing HIV medication once will not change U=U if your HIV load is still undetectable. Adherence to medication schedule is important, and U=U depends on not regularly missing HIV medication, but a stable undetectable viral load will not change if the occasional dose is missed.