During its short but painful existence in humans, HIV/AIDS has thwarted efforts at prevention. Vaccines have proven elusive; changing human behaviors that spread the disease is never as easy as we'd like. HIV in particular is wrapped in a complicated web of women's rights, sexual mores, and a fraught debate over family planning. Which is precisely why a new study, released by the U.S. National Institute of Health on Thursday, could change everything. Treating HIV patients with anti-retrovirals early into their infection, the study found, can prevent up to 96 percent of HIV transmission. That's as high as anyone could ever hope to get with a vaccine.

Ninety-six percent efficacy would be a headline no matter what the debate. But in the  context of the HIV/AIDS debate, this is monumental because it unites two often-opposed ideologies about how best to respond to the disease: treatment or prevention. The U.S. President's Emergency Plan for HIV/AIDS, known as PEPFAR, favored the former, extending anti-retroviral access to 2.5 million people who didn't have it before. When the Barack Obama administration came into office, they wanted to emphasize prevention at least as much or more. As I wrote last summer, that tweak in policy started an advocacy war. 

Why the differences of opinion? For many of the advocates of treatment, this was a way to avoid stepping into the internal U.S. debate  about birth control. Preventing HIV infections usually includes condoms, something that the political right has always found distasteful to support -- at least without a heavy emphasis on abstinence. Prevention advocates meanwhile argued that this was a short-sighted strategy. Providing people with life-saving drugs was great, but it wasn't going to stop the epidemic from growing. Ever.

If the results of this new study hold, however, those two sides of the HIV equation will be joined. Treatment will be prevention, and the best prevention, treatment. The question may have answered itself. The politics and the science will suddenly agree over the most effective public health response. 

So the only catch now? The cost. Under the Obama administration's new Global Health Initiative, funding for anti-retrovirals is growing at a much slower pace than it did in the previous half-decade. The pressure will be on now more than ever to ratchett that up.