Needle Exchange

University of Pennsylvania researcher Philippe Bourgois studies how slight variations in drug use affect infection rates. He says Philadelphia's strong network of people spreading needles from the exchange plays a big role.

"You get this extraordinarily efficient distribution of needles, exactly where they need to be at the right time," he says. "And so that's what basically, I think, prevents a much worse spread of HIV."

Bourgois takes the-long term view. He points out that many of the people who hit rock bottom in this neighborhood will recover — and if access to clean needles can keep them safe until they do, they might be able to live the rest of their lives without the burden of another illness.Article