Over the years, many medical researchers have tried to solve this deadly conundrum. Some point to biology, some to behavior and some to just plain bad luck. The inquiry, however, has been hindered by the nature of the disease. "AIDS is not an event, or a series of them; it's a mirror held up to the cultures and societies we build," Nolen writes in her introduction. "The pandemic, and how we respond to it, forces us to confront the tricky issues of sex and drugs and inequity."