An HIV study that suggested antiretroviral drugs can prevent transmission, as well as treat the virus is being singled out as the most important scientific breakthrough of 2011 by a scientific journal.

The study, HPTN 052, showed that when people infected with HIV take antiretroviral drugs, they are 96 per cent less likely to transmit the virus to someone else. Calling it the 2011 Breakthrough of the Year, the journal Science said "the results have galvanized efforts to end the world's AIDS epidemic in a way that would been inconceivable even a year ago."

Prior to the publication of the study, researchers had been skeptical ARV therapy would reduce transmission of HIV. It had only been shown to reduce the amount of the virus in an infected person’s body.

The study was begun in 2007 with the enrollment of 1,763 heterosexual couples from Brazil, India, Thailand, the United States, Botswana, Kenya, Malawi, South Africa and Zimbabwe. In each couple, one person was HIV positive. Half of the participants were given ARV and half were not — unless they began developing AIDS. When the researchers realized that ARV treatment was cutting transmission of the virus dramatically, they ended the trial early so that the study participants could all begin ARV therapy.

The study’s findings appeared in the August 11 issue of the New England Journal of Medicine.

"This [HPTN 052 trial] does not mean that treating people alone will end an epidemic," wrote Science author Jon Cohen. "But, combined with three other major biomedical preventions that have proven their worth in large clinical studies since 2005, many researchers now believe it is possible to break the back of the epidemic in specific locales with the right package of interventions."

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 the 'treatment as prevention' findings of the study into their policy guidelines for battling the AIDS epidemic, according to Science authors.