TasP stands for "Treatment as Prevention.” Here’s where the term comes from and what it means.

Treatment for someone who is HIV-positive includes medications that act to suppress the virus to the point where the person’s “viral load” is “undetectable," meaning there is so little virus that it's not detectable with laboratory tests, even though the person is still HIV-positive.

HIV transmission within sero-different couples (couples where one partner is HIV-positive and the other is HIV-negative) has been studied extensively. As a result, we now know that someone whose viral load is undetectable and has been undetectable for at least six months is not capable of transmitting HIV through sex, even through anal or vaginal sex without condoms. This idea is frequently expressed as #U=U, or "undetectable equals untransmittable." This is no longer a controversial idea: it has been endorsed by more than 600 organizations in 75 countries.

Effective treatment for people who are HIV-positive also protects their HIV-negative sex partners from HIV. That’s where the term “Treatment as Prevention” comes from.

In the PARTNER study, which has involved almost 800 couples, both gay and straight, there have been zero transmissions of HIV within couples from a partner with an undetectable viral load in what was estimated as 70,000 occasions of condomless intercourse. Transgender men and women were not included in the PARTNER study.

At the community level, TasP and PrEP can both play a major role in reducing the number of new HIV infections.

Remember:

• TasP refers to treatment for HIV-positive people. It helps to keep them healthy and reduces the likelihood that they can transmit HIV to others.
• PrEP refers to a medication and testing regimen for HIV-negative people that reduces the risk of acquiring HIV from someone who is positive.

Just as a positive person cannot be on PrEP, a negative person cannot be on TasP.