The spread of HIV may have an end in sight even for couples who have sex without using condoms, a groundbreaking study has found.The discovery was made following a study which monitored nearly 1,000 gay male couples across Europe over a period of eight years, where one partner was HIV-positive and receiving antiretroviral treatment (ART), and the other was HIV negative, the study published in The Lancet, found.There were no cases of transmission of the infection to the HIV-negative partner during sex without a condom because the virus was being suppressed by the drugs, the research found. However, 15 of the men were infected with HIV during the eight-year period, but DNA testing revealed that this was through sex with someone other than their partner who was not being treated for HIV, meaning that a third of the non-infected participants were having sexual relations outside of their current relationship."Our findings provide conclusive evidence for gay men that the risk of HIV transmission with suppressive ART is zero,” Alison Rodger of University College London, who co-lead the research explained. "It’s brilliant – fantastic. This very much puts this issue to bed."“They support the message ... that an undetectable viral load makes HIV 'untransmittable,'" she continued. "This powerful message can help end the HIV pandemic by preventing HIV transmission, and tackling the stigma and discrimination that many people with HIV face."Researchers estimate that ART prevented about 470 HIV transmissions within couples during the eight year study period.Rodger said that there needs to be “increased efforts ... [that] focus on wider dissemination of this powerful message and ensuring that all HIV-positive people have access to testing, effective treatment, adherence support and linkage to care to help maintain an undetectable viral load.”There are almost 40 million people worldwide living with HIV, of whom 21.7 million - some 59% - are on antiretroviral treatment. Of those affected by the virus worldwide, 1.8 million are children.Despite its success, the researchers found there were limitations to the treatment, including that the average age of the HIV-negative men was 38. Most HIV transmissions occur in people aged under 25.Commenting on the study, Dr Myron Cohen, director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill, said that this research shows that "ART leads to good health."“It is not always easy for people to get tested for HIV or find access to care; in addition, fear, stigma, homophobia and other adverse social forces continue to compromise HIV treatment,” he said. “Diagnosis of HIV infection is difficult in the early stages of infection when transmission is very efficient, and this limitation also compromises the treatment as prevention strategy.”"The findings demonstrate the universal personal and public health benefits of treatment of HIV," Cohen said. "For the HIV-infected person, the sooner it is started the better."Whether a couple uses condoms or not depends on they type of relationship, he said adding that the data shows that "a person whose HIV has been durably suppressed with ART will not transmit HIV."