Undetectable = Untransmissable


Undetectable = Untransmittable

You Can’t Pass It On

Did you know that having an undetectable viral load on HIV treatment (ART) stops HIV transmission?

ART is not only good for your health – it also protects your partners.

U=U means that you don’t need to use condoms if you were only using them to stop HIV transmission.

Leading UK doctors and researchers strongly support the U=U statement.

“There should be no doubt that a person with sustained, undetectable levels of HIV in their blood cannot transmit HIV to their sexual partners.”

Professor Chloe Orkin, Chair, British HIV Association


UK guidelines state that HIV doctors should talk to all their patients about how ART stops transmission.

What is U=U?

U=U stands for:

Undetectable = Untransmittable

It means that someone with an undetectable HIV viral load on ART cannot transmit HIV, even without using condoms or PrEP.

What does U=U involve?

This protection from ART depends on:

  • Taking ART every day.
  • Having undetectable viral load for at least 6 months.
  • Continuing to take your meds every day.

How can U=U not be a risk?

The quick answer is when HIV viral load is undetectable there is too little virus in sexual fluids for an infection to occur.

Any risk of sexual HIV transmission relates to viral load and being undetectable reduces this risk to zero.

Does U=U work with all HIV drugs?

Yes. Any ART that makes viral load undetectable will mean U=U.

Does U=U work for everyone?

Yes. The PARTNER studies included both gay and straight couples.

In straight couples sometimes the man was positive and in others the woman was positive.

Does U=U work for all types of sex?

Yes. The PARTNER studies collected information about the numbers of times people had oral, vaginal or anal sex. It also asked whether the negative partner was active or passive and whether there was ejaculation.

PARTNER reported zero transmissions for all situations.

Does this mean I can stop using condoms?

Whether you use condoms is a personal choice. Or a mutual choice with your partner.

Condoms reduce the risk of many STIs and they can effectively prevent pregnancy.

But if HIV is the only concern, then in the context of U=U, there is no reason to continue to use condoms.

My partner still wants to use condoms?

Whether your partner is HIV positive or HIV negative, they have to decide what is right for them.

They might want to use condoms for other reasons, or they might still worry about HIV transmission.

Sometimes it takes time for someone to accept new evidence, especially after using condoms for many years.

Do STIs affect U=U?

Based on the PARTNER study, U=U still works if, without realising it, one or both partners has an STI.

It is important to monitor and treat STIs, but they are unlikely to affect U=U.

Is U=U widely accepted?

Yes, most leading HIV scientists and doctors now agree with the U=U statement.

This includes the British HIV Association (BHIVA), the International AIDS Society (IAS) and the US Center for Disease Control (CDC).

Will my doctor know about U=U?

Hopefully, yes. U=U has been headline news for at least two years. U=U is included in the BHIVA Standards for HIV Care (2018).

If your doctor doesn’t tell you about U=U, then ask them.

How long does viral load need to be undetectable?

Guidelines recommend having an undetectable viral load for six months before relying on 100% protection from U=U.

This cautious approach is why guidelines refer to being on stable ART.

What if I miss my meds?

Missing your meds once will not change U=U.

But missing meds for 2-3 days might be enough with some combinations for viral load to become detectable.

Good adherence is essential for U=U.

What about viral load blips?

Sometimes viral load can “blip” just above 50 copies/mL.

Blips that stayed below 200 copies/mL did not affect the PARTNER results.

How do we know U=U is so effective?

Researchers have known for over 20 years that ART reduces all transmission risks. But it is only recently that the zero risk has been proved.

The PARTNER studies included couples where one partner was HIV positive on ART and the other HIV negative.

The positive partner needed to have an undetectable viral load and the couple needed to be having sex without condoms.




viral load means HIV IS


In PARTNER 1, couples (both straight and gay) had sex more than 58,000 times without condoms.

In PARTNER 2, in gay men only, couples had sex more than 77,000 times without condoms.

There were no linked transmissions in either study.

Other research includes the Rakai, HPTN 052 and Opposites Attract studies. It also includes the Swiss Statement that first published information about the risk being zero in 2008.

These and other studies are discussed in this online article.

The evidence for U=U: why negligible risk is zero risk


Does U=U apply to breastfeeding?

Although an undetectable viral load on ART also reduces the risk from breastfeeding, it doesn’t reduce this risk to zero.

The have been cases where babies have become HIV positive from breastfeeding, even when the mother had an undetectable viral load.

Further information

The international U=U campaign raises awareness about this benefit from ART.

Currently, more than 720 organisations have joined from over 90 countries.


i-Base has more information on U=U, including a longer version of this factsheet.


* www.i-Base.info Undetectable = Untransmittable /u-equals-u * Produced by i-Base for Kobler@CWH (September 2018) www.i-Base.info

www.i-Base.info September 2018

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