David Wilson, an expert associated with the University of New South Wales in Sydney, says that a computer analysis of rates of HIV transmission from individuals with different levels of the virus in their blood has shown that infection can still occur, and that condoms are still essential.
He says that the incidence of HIV can increase four-fold among the couples in just 10 years if groups of couples, wherein the infection in HIV-infected partners is controlled by drugs, stop using condoms.
The researcher ran the computer simulation to find out what would happen if people with 10 copies of HIV per millilitre of blood - a level that indicates that antiretroviral therapy has effectively controlled the infection - had unprotected sex 100 times each year.
He observed that over the 10 years, there would be 3524 new male-to-male HIV infections in a population of 10000 couples, 425 new male-to-female transmissions in a population of 10000, and 215 new female-to-male transmissions.
"Those are four-fold increases compared to the incidence with current condom use," New Scientist magazine quoted him as saying.
Jonathan Anderson, a general practitioner with a special interest in HIV at the Carlton Clinic in Melbourne, Australia, and president of the Australasian Society of HIV Medicine, said: "Antiretroviral drugs can augment condom use, but this study shows that it would be a disaster if they replaced them as the key preventative strategy."
A research article in the journal The Lancet says that several western countries, including Australia and the UK, have seen large increases in HIV transmission rates in the past decade, despite the widespread use of antiretroviral drugs.
The report adds that a contributing factor is thought to be a fall in the use of condoms, as HIV infection is increasingly seen as a disease that can be managed with drugs, rather than a death sentence.