Potentially misleading advice contained in a statement from the Swiss Federal Commission for HIV/AIDS may quadruple the number of HIV cases, researchers at the University of New South Wales (UNSW) have warned.
According to experts from the Swiss Federal Commission for HIV/AIDS, people with HIV receiving effective antiretroviral treatment can't transmit the virus to their HIV-negative partner through sexual contact.
Now, the new study, conducted by UNSW's National Centre in HIV Epidemiology and Clinical Research (NCHECR), has cast a doubt on these conclusions.
The study also found potential legal implications for people who believe themselves to be non-infectious but go on to have unprotected sex and infect their partner.
It also 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 study is based on mathematical modeling in a population of 10,000 couples where one is HIV positive and the other is HIV negative.
It showed 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," Dr Wilson said.
Dr Jonathan Anderson, the president of the Australasian Society for HIV Medicine, who is also based at NCHECR, said: "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."
"This may be confusing. Antiretrovirals can complement consistent condom use but replacing condom use with medications may end in disaster," he added.
Other factors that increase HIV transmission risk 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," Dr Anderson.
"We are concerned that there may not be the same behaviour if people believe themselves to be non-infectious," he added.
The study is published in The Lancet.