This is the VOA Special English Health Report.

The journal Science chose an AIDS study as the twenty-eleven "Breakthrough of the Year." The study found that antiretroviral drugs can greatly lower the risk of spreading HIV, the virus that causes AIDS. It showed that infected people with early treatment were ninety-six percent less likely to infect their partners.

The study was a clinical trial known as HPTN 052. Myron Cohen led an international team that began the study in two thousand seven and announced the results last May. But Dr. Cohen says the work really began twenty years ago.

MYRON COHEN: "We had a strong suspicion based on all the biological studies we had done that when we treat people and lower the concentration of HIV in the blood and secretions, we were rendering them less contagious. But we didn't understand the magnitude of the benefit. It blows a gigantic wind behind the idea that treatment will serve as prevention."

Dr. Cohen is director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill. The National Institute of Allergy and Infectious Diseases paid for the study.

The study involved heterosexual couples in nine countries in Africa, Asia and the Americas. The results have already had an effect on government policies. Those changes include treating HIV-infected people when their immune systems are still relatively healthy.

MYRON COHEN: "This particular 052 study in the last six months has generated policy changes at the level of the United States and the World Health Organization and UNAIDS. And it's inspired new community-based clinical trials that are just about to be launched that apply the scientific discovery. So when you do a single study and it receives so much recognition, and then seems to inform policy in a dramatic way, you think, OK, this was twenty years well-spent."

Dr. Cohen says the study results will be wasted unless they are linked to other areas of HIV treatment and prevention.

MYRON COHEN: "So the 052 study kind of lends itself to understanding that if we don't know who's positive and negative, there's no benefit. If people aren't linked to care, there's no benefit. If they aren't provided drugs, there's no benefit. If they receive the drugs but don't take the pills, there's no benefit. So this cascade is now the focus of our attention."

AIDS activist Mitchell Warren was among those who welcomed the results.

MITCHELL WARREN: "Treatment is prevention. And that becomes a fundamentally different conversation because for many years debates have waged whether we should do treatment or prevention. And the results of the HPTN 052 study actually affirm once and for all that treatment is prevention."