Those infected with HIV are way less likely to pass on the virus to sexual partners if they take oral antiretroviral drugs before their immune systems are compromised, a series of studies supported by the National Institutes of Health shows.

The studies -- including two conducted in Thailand and Malawi by Johns Hopkins Bloomberg School of Public Health researchers -- involved 1,700 mostly heterosexual couples where one partner was infected but realtively healthy.

“These data conclusively demonstrate that beginning HIV treatment early is a natural form of HIV prevention,” said David Celentano, principal investigator for the Thailand study site and the Charles Armstrong Chair and Professor of Epidemiology at the Bloomberg school, in a statement.
The data showed that the drugs reduced transmission by 96 percent, an unprecedented level of impact.

The studies were conducted at 13 sites around the globe. Only 39 infections were found among previously uninfected partners. There was only one case of HIV infection among couples where the HIV-infected partner had begun drug therapy immediately.

“Previous data about the potential value of antiretrovirals in making HIV-infected individuals less infectious to their sexual partners came largely from observational and epidemiological studies,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Disease, in a statement. “This new finding convincingly demonstrates that treating the infected individual—and doing so sooner rather than later—can have a major impact on reducing HIV transmission.”