Both drugs and condoms needed to stop HIV: study

HONG KONG (Reuters) - HIV infections could quadruple over 10 years if HIV-positive people who are taking antiretroviraldrugs become complacent and stop using condoms, researchers in Australia warned.

The warning, published in The Lancet, comes after the Swiss Federal Commission for HIV/AIDS said in a controversial statement earlier this year that HIV-positive people on effective treatment were sexually non-infectious.

But the Australian researchers stressed that while the risk of transmission from people on effective therapy was low, it was unlikely to be zero.

"Factors such as incomplete adherence to therapy or the presence of other sexually transmitted infections could increase the risk of HIV transmission," they wrote.

"A false sense of security might lead to reductions in condom use, as was documented in a behavioral study among men who have sex with men in Australia."

HIV infections have been rising among homosexual men in a number of countries in recent years despite high treatment rates -- something often attributed to reductions in condom use.

Using mathematical models, the team at the National Centre in HIV Epidemiology and Clinical Research in Sydney showed that, while the risk of HIV transmission by people on treatment was fairly small for each sexual contact, that risk would be substantial over large numbers of sexual contacts.

They based their calculations on 10,000 couples -- one partner being HIV-positive -- having 100 unprotected sexual encounters a year over 10 years.

"The expected number of HIV infections would be 215 for female-to-male transmissions, 425 for male-to-female transmission, and 3,524 for male-to-male transmission, corresponding to an increase in incidence of four times compared with incidence under current rates of condom use," they wrote.

Jonathan Anderson, president of the Australasian Society for HIV Medicine, said the Swiss advice was misleading.

"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," said Anderson, who did not participate in the study.

"Antiretrovirals can complement consistent condom use but replacing condom use with medications may end in disaster."

(Reporting by Tan Ee Lyn; Editing by Alex Richardson)