People infected with the Aids virus who took antiretroviral drugs cut the risk of spreading the infection to their uninfected sexual partner, US government researchers said.

The findings also suggest that the protection is strongest when patients take the drugs as soon as possible.

'The findings of this study strongly indicate that treating an individual with antiretroviral drugs sooner rather than later can have a significant impact on reducing the risk of transmitting HIV to their sexual partner,' Dr Anthony Fauci of the National Institute of Allergy and Infectious Diseases, told reporters in a telephone briefing.

The results are the first from a major randomised clinical trial to show that treating an HIV-infected person with drugs can cut the risk of sexual transmission of HIV to an uninfected partner.

Antiretroviral drugs are used in combination to try to suppress the human immunodeficiency virus and stop the progression of disease caused by HIV. HIV is classified as a retrovirus.

The clinical trial had been scheduled to end in 2015 but the findings were released early because the treatment worked so well.

An independent panel looking at the interim results found clear evidence that HIV-infected individuals with relatively healthier immune systems who took a variety of anti-HIV drugs substantially cut reduced HIV transmission to their partners. - Reuters