As a HIV-positive man, 32-year-old Brent is familiar with the stigma surrounding the perceived risks of transmission with sexual partners who do not have the virus.

He has been HIV positive for seven years and took part in a significant Australian-led study analysing the transmission risk among homosexual couples with differing HIV status.

In what has been described as "life-changing news" for gay male couples where one partner is HIV positive, the study found the virus was not transmitted to their partners, if they took daily anti-viral medication that made the viral load undetectable.

Brent, who asked for his last name to be withheld, said he was already comfortable having sex without a condom because an earlier smaller study had shown similar results, and he was strict about taking his medication every day.

"For many years ... people with HIV have felt stigma in different ways and have been viewed by doctors or other community members as potential passers-on of something which is quite serious," he told the ABC.

"This changes that and as a HIV-positive person anyway, it takes away that fear and that stigma around passing it on and everything that has been attached to that."

Study one of the largest of its kind

Researchers said the findings were "life changing" for couples with differing HIV status. ( Centres for Disease Control and Prevention )

Conducted by the University of New South Wales' Kirby Institute, the study is said to be the largest of its kind, following more than 350 homosexual couples from Australia, Brazil and Thailand over four years.

It found HIV-positive men who were on daily anti-retroviral treatment that made the virus undetectable did not transmit HIV to their partners.

During the course of the study, participating couples reported almost 17,000 acts of anal intercourse without a condom, none of which resulted in HIV transmission.

Chief investigator Professor Andrew Grulich from the Kirby Institute said it was "pretty life changing for couples where one is HIV positive and the other negative".

"The evidence is now clear that a person with undetectable viral load will not transmit the virus," he said.

"This is a massive relief and help in reducing anxiety for these couples and means undetectable viral load is up there in condom use in eliminating HIV transmission in those couples.

"For many years being HIV positive has been associated with enormous stigma and there still is.

"These results show that a person with HIV on treatment with undetectable viral load will not transmit HIV, so there should be no reason to fear a person with HIV, and there should be no reason why there should be any stigma against a person with HIV."

The study's findings have been presented to the International Aids Society Conference in Paris.