Plus Undetectable

Undetectable really does mean Untransmissible U=U

We now have clear, high-quality evidence which confirms without doubt that a person who is taking effective treatment and has sustained undetectable levels of HIV in their blood cannot pass HIV onto their sexual partners. This evidence has been building over the past decade or more. Several well designed, large scale studies recruited heterosexual and gay couples who didn’t consistently use condoms throughout the study period. The ground-breaking PARTNER 1 and 2 Study results have provided a significant turning point, with over 600 organisations in 75 countries endorsing the consensus statement which means in practical terms undetectable really does mean untransmissible.

The British HIV Association (BHIVA) endorsed 'Undetectable equals Untransmittable' (U=U) consensus statement In July 2017. BHIVA Chair, Professor Chloe Orkin, said:

“As the UK’s leading voice for HIV health professionals, our backing for U=U is unequivocal. There should be no doubt about the clear and simple message that a person with sustained, undetectable levels of HIV virus in their blood cannot transmit HIV to their sexual partners’’.

“This fact is a testament to the preventive impact of effective HIV treatment and highlights the need to maximise access to treatment in order to minimise and ultimately eradicate HIV transmission. Spreading the U=U message is also an important way to help reduce the stigma experienced by people living with HIV, whose sexual partners may fear infection unnecessarily.”


Detailed below are some of the important science and study information that underpins the undetectable equals un-transmissible statement.

The science of U=U

  • Viral load is a measure of the amount of HIV present in a small sample of blood (recorded as copies per millilitre of blood). When left untreated HIV levels in the blood can become extremely high, sometimes in the millions in the first few weeks following recent infection. High levels of HIV in the blood significantly increases the risk of HIV transmission occurring.
  • Treatment for HIV is usually made up of 3 sometimes 4 drugs often combined in a single tablet, taken once a day, which stops HIV multiplying in the body. When taken as prescribed, treatment is highly effective and keeps HIV effectively ‘locked away’ so it remains at such low levels it cannot be detected by viral load tests.
  • Undetectable viral load means the amount of HIV in the blood is so low that it cannot be detected by tests used to measure it. We also know that when HIV is undetectable in the blood the levels of HIV in pre-cum, semen, vaginal and anal fluids is so low that HIV cannot be passed on to sexual partners.
  • This finding echoed what is called the Swiss Statement, a consensus statement issued in 2008, said that HIV-positive individuals on effective antiretroviral therapy without sexually transmitted infections (STIs) are sexually non-infectious. The statement also went on to say that where the viral load was below 40 copies for 6 months, and there was regular follow-up a person living with HIV cannot transmit HIV through sexual contact.
  • HTPN 052 Study recruited nearly 1800 couples (mostly heterosexual) and followed them for an average of 1.7 years. The study reported in 2011 and demonstrated being on effective treatment reduced the risk of passing on HIV to a regular heterosexual partner by 96%.
  • PARTNER Study recruited just under 1200 couples between 2010 and 2014 which included both heterosexual and gay couples. In this study undetectable viral load was defined as less than 200 copies. There were no linked transmissions within any of the couples, despite there being 56,000 acts of sex without condom use. This study also demonstrated the transmission risk wasn’t increased where couples also acquired other STI’s.
  • PARTNER 2 Study continued to recruit a further 450 same sex males couples (total of 950 over both PARTNER 1 and 2,) to get a better understanding on the impact of anal sex and risk of transmission. The final results of this study were published in July 2018. The study found no transmissions between gay couples where the HIV-positive partner had a viral load under 200 copies, despite there being around 77,000 acts of sex without condom use.
  • Opposites Attract Study enrolled 358 same sex gay male couples in Australia, Thailand and Brazil also reported zero transmissions during the study period where the positive partner was on effective treatment and had a viral load below 200. This provided further high-quality evidence to support the statement that gay men living with HIV, who have undetectable viral load cannot pass HIV onto their HIV negative partners.

What does U=U mean for people living with HIV?

  • People living with HIV can feel completely confident when talking to sexual partners and explain in practical terms where they are taking effective treatment and their viral load is consistently undetectable they cannot pass HIV on. This is an important message and has the potential to help change perceptions about HIV.
  • Being on effective treatment and consistently having undetectable viral load can now be described as SAFE sex rather than SAFER sex in the context of HIV. The U=U message is an important way to help reduce the stigma experienced by people living with HIV, whose sexual partners may fear they will get HIV.
  • Sometime people taking effective treatment experience ‘blips’ where the viral load becomes detectable above 50 and then returns back to undetectable when retested. A blip between 50 - 200 can be considered to be undetectable. This is because the benchmark undetectable viral load used in the PARTNER studies was defined as being below 200. There have been no cases of HIV transmission occurring where viral load is below 200. Most UK clinics use tests that are sensitive to below either 40 or 20.
  • Condoms offer protection against sexually transmitted infections and are an effective form of contraception. When thinking about HIV, condoms provide an estimated 95% protection, whereas 100% protection (zero transmissions) has been observed in the studies mentioned above.
  • Fully embracing undetectable viral load concept as a method of HIV prevention is an important milestone for everyone regardless of their individual diagnosis or circumstances. People living with HIV and their partners (be they HIV negative or positive) can enjoy a SAFE and healthy sex life without the fear and anxiety that has so often been the case in the past.
  • People living with HIV who wish to start a family can conceive naturally without the worry of passing HIV onto their partners. The male sperm (not to be confused with semen) and female eggs do not harbour HIV and therefore have no impact on conception. With the correct treatment and care during pregnancy HIV positive mothers give birth to healthy HIV negative babies. This is another big step forward in relation to reproductive health for women and men alike.
  • Healthcare professionals living with HIV who perform exposure prone medical procedures can continue to practice in the knowledge that living with HIV doesn’t restrict their employment opportunities. Yet another milestone in employment equality and normalising HIV in the majority of workplace settings.
  • The secondary benefit of taking treatment as prescribed and remaining undetectable has a significant impact in terms of the public health which will help reduce new HIV transmissions down to zero here in the UK. People living with HIV play a vital role in this and should be recognised and celebrated.

What does U=U mean for people who are HIV negative?

  • Knowing that your partner is taking effective treatment and has undetectable viral load removes any fear associated with having a sexual relationship with someone living with HIV. Avoiding potential partners because they have HIV doesn’t reduce your individual risk of getting HIV. In some circumstances selecting partners who believe they are HIV negative can increase this risk where condoms aren’t consistently used.
  • It’s OK to ask people living with HIV if they are taking treatment and have an undetectable viral load. The official surveillance data for England (2017) confirms that 97% of people on treatment are undetectable. In practical terms, when your sexual partner tells you they have an undetectable viral load you can be confident this is the case. It’s always good to have this conversation as it avoids assumptions being made.
  • PrEP when taken as directed offers very similar levels of protection against HIV that have been observed where people living with HIV who have undetectable viral load. It’s important that you talk to your partner about continued condom use in the context of HIV and neither partner should feel pressurised not to continue to use condoms.
  • If you are currently taking Pre-Exposure Prophylaxis (PrEP), once your partner has been undetectable for 6 months you will no longer need to take PrEP to avoid getting HIV. When making decisions about the continued use of PrEP careful consideration should be given to other sexual relationships you may have with others outside your main relationship.
  • If you wish to start a family and your partner is undetectable you can conceive naturally and be completely confident that you won’t get HIV. With correct treatment and care during pregnancy HIV positive mothers give birth to healthy HIV negative babies. This is another big step forward in relation to reproductive health for women and men where one or both partners are living with HIV.
  • Treatment for HIV doesn’t provide protection from sexually transmitted infections (STI’s). Condoms provide a good level of protection against HIV, which has always been described as SAFER sex. Condoms also provide an effective form of contraception, which is an important consideration aside from HIV.
  • Treatment as prevention (U=U), PrEP, condoms and regular testing provide all the tools you need to help you remain HIV negative whilst enjoying full and healthy sex life.

You can find out more information on U=U HERE