Questions About U=U: What, When, Who, Why

U=U: Undetectable viral load equals untransmittable HIV

Table of Contents

The following questions provide more information about why an undetectable viral load stops HIV transmission (U=U).

What Is U=U?

U=U is an abbreviation for: Undetectable = Untransmittable

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

U=U is also part of an international campaign to raise awareness about this benefit of ART. Currently, approximately 600 organisations have joined from 75 countries.

What Does U=U Involve?

The protection from treatment (ART) depends on:

  • Being on stable ART for several months.
  • Having undetectable viral load for at least three months.
  • Continuing to take meds every day without missing doses.

Related: "U=U": What's It All About?

How Can Someone Not Be Infectious?

The quick answer is because when HIV viral load is undetectable (less than 50 copies/mL) there is too little virus for an infection to occur.

Even though someone on ART is still HIV positive, there is not enough HIV for transmission to still be a risk.

Most infections need a certain quantity or concentration of virus for transmission to occur. For example, viral load might need to be above 500 copies/mL to be infectious.

HIV is already a very difficult virus to catch and being on ART reduces this risk to zero.

Does It Matter Which Drugs Someone Takes?

No. The types of HIV drugs are not important.

U=U only relates to whether viral load is undetectable.

Any ART that does this is good.

Does U=U Work for Everyone?

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

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

One third of the couples were gay men.

Does U=U Work for All Types of Sex?

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

PARTNER reported zero transmission for everything.

This includes the highest HIV risk -- ie when the negative partner was receptive for anal sex.

Does This Mean I Can Stop Using Condoms?

Whether or not you use condoms is a personal choice. Hopefully this is a mutual choice with your partner. Condoms are effective at stopping many STIs and they are an effective contraceptive to stop pregnancy.

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

In the context of U=U, condoms don’t have any further impact on reducing the risk of HIV transmission.

For people who are happy using condoms for other reasons, this will still be an important choice.

My Partner Is HIV Positive and Doesn’t Trust U=U or Stopping Condoms?

Your partner has to come to their own decision about 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 if they have been using condoms for many years.

My Partner Is HIV Negative and Doesn’t Trust U=U or Stopping Condoms?

Your partner has to come to their own decision about 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 they have been using condoms for many years.

Is U=U Now Widely Believed?

Most leading HIV scientists and doctors now agree with the U=U statement.

These experts are all convinced by the increasing evidence from many different studies.

Scientists are trained to be cautious people. They need to be convinced by evidence before making factual statements. Although it took a long time for the evidence for U=U to be widely accepted, leading HIV doctors in every country now recognise and support U=U.

For example, Professor Chloe Orkin, chair of the British HIV Association (BHIVA) has been quoted many times:

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

Similar statements have been made by the International AIDS Society (IAS) and the US CDC.

Do STIs Affect the Zero Risk?

U=U still works if, without realising it, one or both partners has an STI.

The PARTNER study included couples where STI rates were reported, usually in the context on an open relationship. Although routine check-ups for STIs are important, with treatment if needed, there were still no HIV transmissions.

It is only when ART is not used that the risk of HIV transmission become higher if either partner has an STI.

Will My Doctor and Health Workers Know About This?

Hopefully, yes. This has been headline news for several years now.

U=U is included in HIV treatment guidelines.

However, just as leading experts took time to accept the evidence, some doctors are slow to discuss U=U with all their patients.

For many years, condoms were the main way to protect against HIV. This is no longer the case. New studies prove that both U=U and PrEP are more effective than just relying on condoms.

How Long Does Viral Load Need to Be Undetectable?

The risk of transmission steadily get lower as viral load drops on ART. But viral load needs to be undetectable for the risk to become zero.

This usually takes between 1 to 3 months after starting ART for most people. If viral load is very high when starting ART, it can sometimes take longer.

As viral load sometimes takes longer to become undetectable in genital tissue and genital fluids, guidelines recommended waiting a couple of months after viral load is undetectable in blood.

This is just an estimated cautious approach, but is the reason guidelines for U=U refer to being on "stable ART". this means having had and undetectable biral load for 203 months before the U=U risk becomes zero.

What If I Forget to Take My Meds One Day?

Missing one single dose of ART will not change U=U.

This is because viral load will still be undetectable.

Good adherence is important, but it you would probably need to miss HIV meds for 2-3 days before viral load becomes detectable.

If you do miss ART for several days, it is important to check your viral load is still undetectable before relying agin on U=U.

U=U depends on not regularly missing doses of HIV meds.

How Do We Know Undetectable Viral Load Is So Effective?

Researchers have known for over 20 years that ART reduces the risk of transmission.

It is only in the last few years however, that it became clear that transmission is stopped completely.

In 2007, some doctors were already so convinced that they published a document called the Swiss Statement. Since then several studies have provided more evidence.

One of the most important of these was the PARTNER study. This enrolled 900 serodifferent couples (where one partner was HV positive and the other HIV negative). The positive partner needed to be on ART with an undetectable viral load and the couple needed to be having sex without condoms. Approximately one-third of the couples were gay men.

PARTNER reported zero linked HIV transmissions after more than 58,000 times that couples had sex without condoms.

In the few cases where the negative partner did become HIV positive, this was always from outside the relationship. The study was able to prove this by comparing the structure of the different viruses.

What Is the Difference Between "Zero" and "Very Low"?

The difference between zero risk and a very small risk is complicated. Technically, it is not possible to prove something will not happen.

Instead, the scientific approach is to define a possible risk, however small. For example, 1 in a million etc. This is easy to do with low risk activities, but with zero risk activities, there is nothing to measure.

In these cases a very small theoretical risk is effectively zero. This is why scientists are happy to say the risk is now zero.

The risk is not "greatly reduced", it is not "negligible" it is zero.

Since the Swiss Statement was widely publicised in 2007 there have been no proved case reports of HIV transmission with undetectable viral load.

Even if in the future, a case is reported, the absolute risk would be so low for this to still be effectively zero.

What Is the Evidence to Support U=U?

The evidence for U=U is discussed in detail in the following article. This cover many different types of studies from the last 20 years.

_The evidence for U=U (Undetectable = Untransmittable): why negligible risk is zero risk

Individual results from key studies and the Swiss Statement are included below.

_ZERO: no linked HIV transmissions in PARTNER study after couples had sex 58,000 times without condoms (2016)

_Q&A on the PARTNER study: how to interpret the zero transmission results (2016)

Gay men with undetectable viral load do not transmit HIV: Opposites Attract study supports U=U (2017)

Treatment is prevention: ARV treatment in HPTN-052 reduces transmission by at least 96%: single transmission in treatment arm occurred prior to viral suppression (2011)

HPTN 052: no HIV transmissions on effective ART -- long-term follow-up (2015)

The Swiss Statement (2007)

[Note from TheBody: This article was originally published by HIV i-Base on May 3, 2018. We have cross-posted it with their permission.]