A man carrying HIV/AIDS has "zero" risk of transmitting the virus to his non-infected partner if he's being successfully treated for the disease, a landmark new study has found.
Nearly 1,000 serodifferent — when one partner has HIV/AIDS and the other doesn't — gay male couples across Europe took part in the eight-year study published in The Lancet journal.
It shows the spread of the AIDS virus can be contained, even through condomless sex, if the HIV-positive partner is successfully treated with antiretroviral therapy (ART).
The researchers estimate that "approximately 472 transmissions" were prevented because of ART during the length of the study. Fifteen men did contract the virus, however, their infections were with strains of HIV acquired from another sexual partner.
Alison Rodger, a professor at University College London, who co-led the research, said that the "findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero."
The results are similar to those previously generated for heterosexual couples in the same circumstances.
According to UNAIDS, the United Nations' agency tasked with coordinating a global effort to combat the epidemic, 36.9 million people were living with HIV/AIDS worldwide in 2017. Of those, 75% were aware of their status and 59% — 21.5 million — had access to antiretroviral therapy.
But over nine million people did not know of their status and/or lacked access to testing services.
The vast majority of those living with HIV live in middle-or-low income countries with 53% residing in eastern and southern Africa. More than 2 million — or 6% — are in Western and Central Europe and North America.
Rachel Baggaley, the World Health Organization's coordinator for HIV prevention and testing, said this study shows "clear and consistent evidence" that HIV transmission can be suppressed if seropositive people have access to ART.
"Increasing access to HIV testing (and) ART ... remains critical for individuals and is central to the HIV public health response," she added.