Antiretroviral treatment is now being hailed as a prevention tool by scientists who argue that people on ARVs with undetectable viral loads are very unlikely to infect others.

Evidence for this comes from a Canadian study which, using a mathematical model, predicts that if ARVs reached all those who needed them, this would reduce the annual rate of new HIV infections by 60 percent.

“We’ve known for some time that the expansion of coverage with highly active ARV therapy could help to reduce the number of new infections. However, we were amazed at the actual number of new infections that can be potentially averted by expanding access to treatment,” said Dr Julio Montaner, who led the study.

Stephen Lewis, former United Nations AIDS Envoy, endorsed the link between ARV treatment and prevention, describing it as a “dramatic and real psychological boost to treatment efforts everywhere”.

In contrast, said Lewis, other prevention efforts were either “in trouble”, such as vaccines and microbicides, or “slow”, such as individual behaviour change.

Meanwhile, the Swiss Federal AIDS Commission on HIV/AIDS has declared that people with an undetectable viral load for more than six months and no sexually transmitted infections, should be considered non-infectious.

According to the Swiss commission, “sex without condoms may pose no realistic risk of HIV transmission from people with an undetectable viral load and no sexually transmitted infections”.

However, results from a large study of 1,750 discordant couples – one HIV positive and the other negative – to further test the infectiousness of HIV positive people with low viral loads will only be known in 2013.

But Dr Walt Senterfitt, an epidemiologist and chair of the Community HIV/AIDS Mobilisation Project (Champ), said he was sceptical about Montaner’s optimism about the effect of an individual’s viral load on the general population.

“The strongest argument for scepticism is the experience of much of the US and Europe, where treatment is relatively widely available, yet HIV incidence remains stubbornly high or is rising,” said Senderfitt.

“At the very least, the relationship of treatment to prevention is not simple or automatic, even under the best conditions.”

Senderfitt added that as many as half of all new infections were from people in “the very early stage of HIV infection when they are highly infectious and unlikely to know of their infection”.

Kerry Cullinan

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