After eight years of follow-up of the so-called serodifferent couples, the study found no cases at all of HIV transmission within couples.





A European study of nearly 1,000 gay male couples who had sex without condoms — where one partner had HIV and was taking antiretroviral drugs to suppress it — has found the treatment can prevent sexual transmission of the virus.

After eight years of follow-up of the so-called serodifferent couples, the study found no cases at all of HIV transmission within couples.

The study proves, the researchers said, that using antiretroviral therapy (ART) to suppress HIV to undetectable levels also means it cannot be passed on via sex.



"Our findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero," said Alison Rodger, a professor at University College London who co-led the research. "Our findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero," said Alison Rodger, a professor at University College London who co-led the research.

She said this "powerful message" could help end the HIV pandemic by preventing the virus' transmission in high-risk populations. In this study alone, for example, the researchers estimate that the suppressive antiretrovial treatment prevented around 472 HIV transmissions during the eight years.

serodifferent heterosexual couples who also did not use condoms. It also found zero risk. The study was published in the Lancet medical journal on Thursday. Its findings add to an earlier phase of the study which looked at HIV transmission risk forheterosexual couples who also did not use condoms. It also found zero risk.

While 15 of the men among the 972 gay couples in this phase did become infected with HIV during the eight years of follow-up, genetic testing showed their infections were with strains of HIV acquired from another sexual partner.

The new findings aren't surprising but are great news nonetheless, said Dr. Darrell Tan, an infectious diseases physician at St. Michael's Hospital in Toronto. He's prescribed and studied suppressive antiretrovial treatment, as well as pre-exposure prophylaxis (PrEP) — medication taken by an HIV negative partner to prevent transmission from happening should they be exposed to the virus.

But antiretroviral therapy and PrEP is expensive and access is uneven across Canada, Tan said.

"The data are so compelling there's not only direct clinical benefits, there's direct preventative benefits as well," Tan said. "We need to have universal access."

The cost of antiretroviral therapy and PrEP as well as stigma of HIV might explain why every year in Canada about 2,400 new cases are reported.

Talking about putting people on antiretroviral medications is one thing, but finding them, ensuring they're tested, starting treatment and staying on it is another, said Dr. Isaac Bogoch, an infectious disease physician at Toronto General Hospital.

"This is often referred to as the cascade of care. And we know that a lot of people who are infected with HIV might be representative of more marginalized populations," Bogoch said. "Some of these individuals might not have had the best interactions with society or with health care. Some groups that are disproportionately affected with HIV might have concombinant (associated with) mental health issues and these all need to be addressed."

Since the start of the AIDS epidemic in the 1980s, more than 77 million people have become infected with HIV worldwide. Almost half of them, 35.4 million, have died of AIDS-related illness.

Rachel Baggaley, the World Health Organization's co-ordinator for HIV prevention and testing, said this latest study "adds to the clear and consistent evidence" that HIV transmission to sexual partners does not occur when someone with HIV is on antiretroviral therapy (ART) and their virus is suppressed.



"Increasing access to HIV testing [and] ART ... remains critical for individuals and is central to the HIV public health

response," she said.

Global health experts say the fight against HIV is at a precarious point, with the annual number of AIDS deaths falling and the number of people getting antiretroviral treatment rising, while the number of new infections is stubbornly high at around 1.8 million new cases per year.