Press statement

UNAIDS welcomes additional evidence that effective antiretroviral therapy stops transmission of HIV

Results from a large-scale European study among serodiscordant gay couples show that adherence to effective treatment prevents transmission of HIV

GENEVA, 3 May 2019—UNAIDS warmly welcomes the PARTNER2 study results that show that HIV transmission does not occur when a person living with HIV is on effective antiretroviral therapy. The study, which enrolled nearly 1000 gay couples in which one partner was living with HIV and the other was not, showed that where the person living with HIV was taking effective antiretroviral therapy and had a suppressed viral load, there was no HIV transmission within the couple.  

“This is excellent news. People living with HIV now have confirmation that provided they take treatment regularly and are virally suppressed, they are not infectious,” said Michel Sidibé, Executive Director of UNAIDS. “This gives a strong, positive message that will help to reduce the stigma around HIV and improve the self-esteem and self-confidence of people living with HIV.”

By the end of the eight-year study, 15 people did become infected with HIV. Virus screening showed that none of the new infections were linked to the HIV-positive partners in the study, but came from a sexual partner outside of the couple. The researchers estimate that within the study, which took place across 14 European countries, around 472 HIV transmissions were averted over the eight years.

UNAIDS hopes that the results will encourage more people to get tested early and take effective treatment. In recent years there has been a huge scale-up in the roll-out and uptake of antiretroviral therapy. In 2017, of the 36.9 million people living with HIV, 59% (21.7 million) had access to treatment and 47% were virally suppressed. Concerted efforts are needed to ensure that all people living with HIV have access to and adhere to effective antiretroviral therapy.

A large proportion of HIV transmission still occurs before people know their HIV status. The risk of HIV transmission is highest in the weeks and months immediately after infection, when the viral load is high and the person who has contracted the virus is unlikely to know their status, is not on treatment and is not virally suppressed. This demonstrates the critical importance of continuing HIV prevention efforts, including condom use and pre-exposure prophylaxis—medicine taken by an HIV-negative person to prevent HIV.


The Joint United Nations Programme on HIV/AIDS (UNAIDS) leads and inspires the world to achieve its shared vision of zero new HIV infections, zero discrimination and zero AIDS-related deaths. UNAIDS unites the efforts of 11 UN organizations—UNHCR, UNICEF, WFP, UNDP, UNFPA, UNODC, UN Women, ILO, UNESCO, WHO and the World Bank—and works closely with global and national partners towards ending the AIDS epidemic by 2030 as part of the Sustainable Development Goals. Learn more at and connect with us on Facebook, Twitter, Instagram and YouTube.


Sophie Barton-Knott
tel. +41 22 791 1697 / +41 79 514 6896


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