A dangerous precedent in HIV

The research from UNSW's National Centre in HIV Epidemiology and Clinical Research (NCHECR) calls into question the conclusions reached by experts from the Swiss Federal Commission for HIV/AIDS that stated that people with HIV receiving effective antiretroviral treatment could not transmit the virus to their HIV-negative partner through sexual contact.

"If the Swiss Commission's conclusions were adopted at a community level and resulted in reduced condom use it would be likely to lead to substantial increases in infection," says Dr David Wilson, a mathematical modeling expert from NCHECR.

The new research which is published in The Lancet also notes potential legal implications for people who believe themselves to be non-infectious but go on to have unprotected sex and infect their partner.

Dr Wilson is the first author on a paper that predicts that HIV transmission over a ten-year period would be four times higher in serodiscordant couples who abandon condom use than if condoms had been used.

The research is based on mathematical modeling in a population of 10,000 couples where one is HIV positive and the other is HIV negative. It found that there would be 215 female-to-male transmissions, 425 male-to-female transmissions and 3,524 male-to-male transmissions in each 10,000 couple group.

"While it is true that the individual risk of HIV transmission per act is fairly small for people on antiretrovirals, the risk of transmission over large numbers of acts could be substantial," says Dr Wilson.

"When the viral load goes down in the blood due to antiretrovirals, it might not go down in the semen or vaginal and anal fluids," says Dr Jonathan Anderson, the president of the Australasian Society for HIV Medicine, who is also based at NCHECR. "This may be confusing. Antiretrovirals can complement consistent condom use but replacing condom use with medications may end in disaster."

Other factors that increase the risk of HIV transmission include incomplete adherence to therapy, changing drug regimes and infection with other sexually transmitted diseases.

"People who are diagnosed with HIV infection tend to reduce their number of new sexual partners, use condoms more consistently and disclose their status to their current partner or partners," says Dr Anderson. "We are concerned that there may not be the same behaviour if people believe themselves to be non-infectious."

Source: University of New South Wales