The risk of passing on the HIV virus is completely eliminated by effective drugs treatment, a landmark study has shown, in a significant boost to the prospects of ending the AIDS pandemic.

A study of nearly 1,000 gay male couples with one partner with HIV who took antiretroviral therapy (ART) found no new cases of transmission to the HIV-negative partner during sex without a condom.

Over the course of the eight-year study, 15 men were infected with HIV, the virus that causes AIDS. But genetic tests showed that the transmissions were a result of the HIV-negative men having sexual relations with someone other than their regular partner.

The report, published in The Lancet medical journal, shows that using ART to suppress HIV virus to undetectable levels renders it incapable of transmission during sex, according to the researchers.

If everyone in the world with HIV knew their status and had access to effective treatment, no new cases would occur, the study suggests.

Alison Rodger, a professor at University College London who co-led the research, told CNN's Hala Gorani that if everyone in the world had access to the right treatment, the virus could be eliminated.

"We've got a way to go to get people easier access to testing and treatment, but if we could get global coverage, then we could really make headway in eliminating the virus," she said.

"It was such a powerful result that we thought we just improve the quality of life for people with HIV."

Rodger said what the study shows is that the risk of transmission is zero with ART treatment "and that's quite new and important."

An earlier study showed that the drugs protected heterosexual couples in which one partner was HIV-positive; the latest research completes the picture, Rodger said. "The question has been definitively answered; there is no need for further research. It's not often we get to say that. Finding ways to get the knowledge in practice is what we need to do next." There was still considerable work to be done to ensure that everyone who has HIV can access testing and treatment, she added.

Other experts welcomed the results. "These important results serve to inspire and challenge us. Timely identification of HIV-infected people and provision of effective treatment lead to near normal health and lifespan and virtual elimination of the risk of HIV transmission," Myron S. Cohen, a professor at the UNC Institute for Global Health and Infectious Diseases at Chapel Hill in North Carolina, who conducted the study of heterosexual couples, wrote in a commentary in the Lancet.

But he cautioned that stigma, homophobia and other social forces have meant that getting tested for HIV and accessing treatment is not always possible, particularly for men who have sex with men. Additionally, diagnosis of HIV in the early stages of the infection is still challenging, compromising treatment as a prevention strategy, Cohen said.

During his February State of the Union address, President Donald Trump announced an ambitious plan to eliminate HIV transmissions in the United States in the next 10 years. Central to Trump's multiagency initiative is the early diagnosis, prevention and treatment of HIV.

While health experts applauded Trump's effort, many have also criticized the White House for cutting funding for HIV/AIDS programs in the past. Millions of dollars were shifted away from HIV/AIDS prevention programs last year.

In March, Trump requested $291 million for the project in his 2020 budget, though this sum is not guaranteed. At the same time, he proposed slashing funding to HIV programs through the President's Emergency Plan for AIDS Relief (PEPFAR) by $1.35 billion overall, according to an analysis by the Kaiser Family Foundation, a nonprofit group that researches health care and other issues.

Still, Cohen expressed optimism about HIV treatment, underlining that antiretroviral drugs have become more effective, reliable, durable, easier to take, well-tolerated and much less expensive.

"The results of the ... study provide yet one more catalyst for a universal test-and-treat strategy to provide the full benefits of antiretroviral drugs. This and other strategies continue to push us toward the end of AIDS."