HEALTH campaigners say a new front has opened in the three-decade war on AIDS after a study among couples showed early use of drugs slashed the risk of HIV infection through sex by 96 per cent. Antiretroviral drugs can deliver a double blow by suppressing HIV in an infected patient and helping to prevent its spread through intercourse. Tasks include encouraging HIV testing and administering early treatment to people with the virus, especially in at-risk population niches such as gay men, intravenous drug users and sex workers. Margaret Chan, director general of the UN’s World Health Organisation, said the study was “a crucial development”. Throughout the history of AIDS, the pendulum of policymaking has swung between treatment, essentially drugs, and prevention, essentially the condom. But this to-and-fro doctrinal debate was challenged in January 2008 by a Swiss researcher, Bernard Hirschel. He ventured that someone who had observed a drug regimen and was shown to have suppressed the virus in his or her blood was no longer an infection risk through sex. Some activists scorned the findings as premature or even irresponsible. But vindication came today with data from the first randomised clinical trial, carried out among “discordant” couples, one of whom had the virus while the other was HIV-negative. The probe was conducted at 13 sites in Africa, Asia and the Americas among 1,763 couples, 97 per cent of whom were heterosexual. In the first group, the HIV-positive partner received anti-HIV drugs immediately; in the second, the HIV-positive partner deferred treatment until he or she had reached a given level of viral infection. The US National Institutes of Health reported when an HIV-infected partner began immediate antiretroviral treatment and adhered to it, there was a 96-per cent fall in HIV transmission. Jean-Francois Delfraissy, director of France’s National Agency for AIDS Research (ANRS), described the study as “a really important moment for public health”. AVAC, a New York-based group for HIV prevention, said the study highlighted the success of the revolutionary drugs that emerged in the mid-1990s and are now a lifeline for millions.