U=U: Science, Not Stigma

Sexual transmission of HIV can be stopped. While there are many barriers to ultimately reaching this goal, one of the most exciting and recently validated concepts resulting from large-scale studies is that of U=U, or Undetectable = Untransmissible.

U=U means that people living with HIV (PLHIV) with a suppressed/undetectable viral load have effectively no risk of transmitting the virus to their sexual partners. The landmark trial of HPTN 052, and subsequent PARTNER, and Opposites Attract studies showed that no linked HIV transmissions were detected between thousands of serodiscordant couples (where one partner is known HIV-positive and one is HIV-negative) as long as the viral load remained undetectable throughout the relationship. This was demonstrated for both heterosexual and homosexual couples, and the greater acceptance of the science has potentially vast implications for personal and public health, social and behavioural norms, and even legal matters.

In order for someone living with HIV to reach undetectable viral load, they will need to be on daily antiretroviral therapy (ART) for at least 3-6 months, and must continue on the medication to maintain viral suppression. Treatment as Prevention (TasP) has been strongly advocated for many years now by HIV specialists and other healthcare providers, but the science and messaging has finally caught up. And for PLHIV, growing awareness and acceptance of U=U will hopefully serve to reduce stigma and discrimination, as well as improve compliance to treatment and follow up.

In 2014, UNAIDS launched the 90-90-90 program which aims to diagnose 90% of all HIV-positive individuals, provide antiretroviral therapy to 90% of the people diagnosed and achieve viral suppression for 90% of those treated by 2020. Current estimates from the Ministry of Health are that only 72% of people living with HIV in Singapore know their status, out of which 89% are on treatment, with the proportion of people on treatment who had achieved viral suppression fairly high at 94%. While the latter two figures are encouraging, more needs to be done to improve HIV testing and diagnosis. Local data shows that only 23% of HIV cases are currently being detected via voluntary screening, while 41% of HIV cases are diagnosed in a late stage.

With over 6,000 people in Singapore currently diagnosed as living with HIV, this means that close to 2,500 are estimated to have the infection without knowing their status. With U=U being a reality, getting at-risk individuals tested and on treatment as early as possible is essential in our fight against HIV. For those who already know their HIV-positive status, there is now additional cause to adhere to ART, as doing so will protect potential future partners from potential transmission.

While U=U is great news overall, there are certain caveats we must remember. For U=U to be considered effective, PLHIV must have an undetectable viral load for a duration of at least 6 months on follow up. Furthermore, studies which have shown that over a quarter of HIV-positive gay and bisexual men in a serodiscordant relationship did not have an accurate understanding of their current viral load, with around 20% of men who believed they were undetectable actually having a detectable viral load. As such, regular condom use and testing is still strongly recommended, as is the wider uptake of Pre-Exposure Prophylaxis (PrEP). It’s also important to note that U=U only applies to HIV infection, so precautions should still be taken against other more common sexually transmitted infections (STIs) such as chlamydia, gonorrhea, and syphilis.

U=U is a simple but important message based on a foundation of scientific evidence. The campaign makes a strong case for adherence to treatment and follow up, and allows PLHIV and the community to understand that they can live long, healthy lives, have children, and enjoy relationships without having to fear passing the infection to others. It will hopefully bring us a few steps closer to achieving the UNAIDS’ 90-90-90 target and help to reduce the stigma still faced by many living with HIV today.


Dr. Jonathan Ti is a GP at DTAP @ Robertson clinic. He has a special interest in sexual health and HIV, and is a co-author of the Community Blueprint to End HIV-transmission and AIDS in Singapore by 2030, and part of the National PrEP Taskforce.

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