The journal Science’s 2011 Breakthrough of the Year is an HIV-prevention study led by UNC’s Myron Cohen. The study showed that early treatment with antiretroviral drugs — that is, drugs that attack retroviruses such as HIV — can effectively prevent the transmission of the virus. The study enrolled “discordant” couples, one of whom carried the HIV virus and one of whom did not. Among these couples, the treatment reduced HIV transmission by at least 96 percent.

The editors at Science said in their announcement that “In combination with other promising clinical trials, the results have galvanized efforts to end the world’s AIDS epidemic in a way that would been inconceivable even a year ago.”

Cohen’s study is proof of a concept more than twenty years in the making. “From the time the first AIDS drugs were developed in the mid-1990s, our UNC team of virologists, pharmacologists, and physicians has been working on the idea that antiretrovirals might make people less contagious,” says Cohen. “By 2000, the UNC study team thought the idea was strong enough to try to prove it.”

U.S. and international organizations such as the World Health Organization, the President’s Emergency Plan for AIDS Relief, and the Joint United Nations Programme on HIV/AIDS have incorporated or soon will incorporate “treatment as prevention” — the strategy proved by Cohen’s study — into their policy guidelines for battling AIDS.