Starting antiretroviral treatment early against HIV is highly effective at preventing sexual transmission of the deadly virus in partners, a new study conducted in nine countries, including India, has found.
Beginning in 2005, the study enrolled 1,763 heterosexual couples ages 18 or older in India, Botswana, Brazil, Kenya, Malawi, South Africa, Thailand, the US and Zimbabwe. Each couple included one partner with HIV infection and one without.
Infected participants were assigned at random either to start antiretroviral therapy right away, while their immune system was relatively healthy, or to delay starting treatment until their immune system weakened or they developed an AIDS-defining illness, consistent with World Health Organisation (WHO) guidelines at the time.
All participants received condoms and counselling on how to protect their partners from sexual transmission of HIV. In 2011, the study investigators at the HIV Prevention Trials Network (HPTN) reported a breakthrough - starting HIV treatment early, reduced the risk of sexually transmitting the virus by 96 per cent over 18 months.
Once the investigators reported their data in 2011, all infected study participants were offered the opportunity to begin antiretroviral therapy right away, and the trial continued for another four years. At the end of the study, 1,171 couples remained in the trial.
Based on additional data gathered since 2011, the new findings show the power of HIV-controlling antiretroviral therapy to reduce sexual transmission of the virus.
"The study now makes crystal clear that when an HIV-infected person takes antiretroviral therapy that keeps the virus suppressed, the treatment is highly effective at preventing sexual transmission of HIV to an uninfected heterosexual partner," said Anthony S Fauci, director of National Institute of Allergy and Infectious Diseases in US.
"For heterosexuals who can achieve and maintain viral suppression, the risk to their partners is exceedingly low," he said.
Only eight cases of HIV transmission occurred in uninfected partners of HIV-infected participants who received antiretroviral therapy.
Four of these infections were diagnosed shortly after the start of treatment. In these cases, the virus most likely was transmitted just before antiretroviral therapy began or right after it commenced, before treatment had fully suppressed HIV replication.