Using computers to model epidemic dynamics with data from South Africa, researchers from the World Health Organization (WHO) showed in theory that universal voluntary HIV testing, with immediate antiretroviral treatment (ART) for those diagnosed positive, could practically halt AIDS in epidemic areas by reducing HIV cases by 95 per cent over 10 years.

The study, conducted by Dr Reuben Granich, of the Department of HIV/AIDS, WHO, Geneva, Switzerland, and colleagues, was published online in The Lancet on 26 November.

According to the authors, by the end of last year, about 3 million people worldwide have been treated with ART, but they estimated another 6.7 million who needed ART went untreated and another 2.7 million people became infected last year.

Using computer-based mathematical models on data from South Africa, and assuming all HIV transmission was heterosexual, Granich and colleagues explored in theory how testing everyone over the age of 15 for HIV every year, and treating infected people with ART straight away, affected the case reproduction rate and long term dynamics of HIV spread in a generalized epidemic.

They found that such a strategy would within 10 years reduce the incidence of HIV in an epidemic population from 20 per 1,000 people to 1 per 1,000, a fall of 95 per cent.

Granich and colleagues also suggested the current endemic phase where most HIV positive adults are not receiving ART could within 5 years rapidly become an elimination phase where most adults with HIV were receiving ART.

They wrote that:

“Instead of dealing with the constant pressure of newly infected people, mortality could decrease rapidly and the epidemic could begin to resemble a concentrated epidemic with particular populations remaining at risk.”

Control of the epidemic would switch focus from offering ART only to those people who most needed it to supporting those already on it, said the authors, explaining that transmission rates would fall to low levels causing the epidemic to steadily decline towards elimination as more people on ART got older and died.

Although other strategies using a combination of preventive measures could reduce the incidence of HIV substantially, Granich and colleagues wrote that their model:

“Suggests that only universal voluntary HIV testing and immediate initiation of ART could reduce transmission to the point at which elimination might be feasible by 2020 for a generalised epidemic, such as that in South Africa.”

Their findings reinforce those of other studies that have suggested rapid scale up of ART could greatly reduce deaths and incidence of HIV, they explained, concluding that:

“Universal voluntary HIV testing and immediate ART, combined with present prevention approaches, could have a major effect on severe generalised HIV/AIDS epidemics. This approach merits further mathematical modelling, research, and broad consultation.”

In an accompanying commentary, one of the WHO authors, Dr Kevin De Cock, who is also based in Geneva, and other colleagues, pointed out that they were not trying to steer policy or give technical guidance, but to highlight the need for more research and debate, especially among countries and stakeholders, about the role of ART in HIV prevention. They suggested for example, that:

“Advantages of immediate treatment on diagnosis could include: simplified clinical management; reduction in the high mortality rates from late diagnosis; control of HIV-associated tuberculosis; and effective prevention of mother-to-child transmission of HIV, including through breastfeeding.”

They also listed some of the barriers to such an approach, whose feasibility would be challenged by:

“Weak health systems and inadequate health personnel; choice of appropriate drug regimens; treatment adherence; drug toxicity; drug resistance and need for durable second and third-line regimens; the logistics, reliability, and acceptability of regularly testing a whole population for HIV infection; and behavioural risk compensation.”

In a second accompanying commentary, Professor Geoffrey P Garnett from Imperial College London, UK, said that the strategy suggested by the study would “reflect public health at its best and its worst”.

“At its worst,” said Garnett, “the strategy will involve over-testing, over-treatment, side-effects, resistance, and potentially reduced autonomy of the individual in their choices of care.”

The infected person might not benefit from testing and being treated early, but people they could potentially infect would. “Who could object to that”, said Garnett, “unless they were recklessly exposing others to infection?”

“It is easy to see how enforced testing and treatment for the good of society would follow from such an argument. Partial success would lead to infection becoming concentrated in those with a high risk, with an increased danger of stigma and coercion,” he warned.

“Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model.”
Reuben M Granich, Charles F Gilks, Christopher Dye, Kevin M De Cock, Brian G Williams.
The Lancet, Early Online Publication, 26 November 2008.

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Sources: The Lancet.

Written by: Catharine Paddock, PhD