The idea of using antiretroviral drugs (ARVs) not only to treat HIV infection but also to prevent new infections, and eventually to eradicate the virus almost entirely, is being hotly debated at the 5th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town, South Africa, this week.
Scientists have long known that ARV treatment can reduce the amount of HIV in an infected person's blood to levels that make transmission unlikely, but the limited numbers of people accessing ARVs means that treatment has so far failed to have a dramatic impact on HIV incidence (the rate of new infections).
A study published in the British medical journal, The Lancet, in January 2009 by leading experts in the HIV/AIDS field, used a mathematical model to explore the effects of testing all adults for HIV once a year and immediately starting everyone who tested positive on ARVs.
Using data from South Africa as an example of a generalized epidemic, the authors found that full implementation of this strategy would lower HIV incidence to less than one case per 1,000 people within 10 years, and reduce prevalence to less than 1 percent within 50 years.
While some in the field have described the "test and treat" model as an unfeasible pipe-dream, others view it as a viable strategy for eradicating the HIV epidemic.
Reuben Granich, a medical officer in the World Health Organization's HIV/AIDS department and principal author of The Lancet study, told delegates on Monday: "There's no reason why we shouldn't visualize that future generations will know about [HIV] through history only."
He argued that well-designed HIV counselling and voluntary testing programmes could reach large numbers of people, and that starting them on ARVs two to four years earlier than current guidelines suggested was not a significant period in the context of life-long treatment; although initially the costs would be higher, over time the dramatic reduction in HIV incidence would bring major cost savings.
|There's no reason why we shouldn't visualize that future generations will know about [HIV] through history only|
However, the recently appointed United States Global AIDS Coordinator, Dr Eric Goosby, has already cautioned that the strategy could result in a conflict between broad public health goals and the health outcomes of individual patients.
"A physician has to do what is in the best interests of an individual patient," and the long-term side effects of ARV treatment might mean it was not always in their best interests to start treatment immediately following diagnosis, he told delegates at the conference.
Calls by many speakers to start HIV-infected patients on ARV treatment earlier, if not immediately, were less controversial - patients who start ARVs after their CD4 cell count has dropped below 350 suffer fewer opportunistic infections and experience lower mortality rates than patients who start treatment at a CD4 count of 200 or less.
The developed world has already raised the threshold for treatment to reflect this, but most countries in sub-Saharan Africa, where the majority of infections occur, have not, citing cost and human resource shortages as the main factors.
Julio Montaner, chair of IAS, warned of "the ever-widening gap between evidence and practice", but Dr Francois Venter, director of the Southern African HIV Clinicians Society, pointed out that the debate about when to start treatment was largely academic in much of southern Africa, where many people still die before ever accessing treatment.
Venter also noted that while the number of people in South Africa testing for HIV had increased dramatically, they still came for treatment when it was dangerously late, suggesting a lack of referral and retention in care post-testing. In Johannesburg's inner city, where Venter works, the average CD4 count when treatment starts is 106.
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