Timothy BrownYou probably remember the story. Brown, who was living with HIV, needed risky, costly stem cell transplants for leukemia. He got the transplants in 2007 and 2008 from a donor who had a genetic mutation that made his cells virtually resistant to HIV. Brown acquired the resistance along with a healthy immune system, and he was declared cured of AIDS—a world first—in 2010.

Since then, the generous and groundbreaking Brown has submitted himself to repeated medical tests to monitor the minutiae of his body's microbiology. Recently, samples of his blood cells and rectal tissue seemed to reveal some fragments of HIV.

However, the viral fragments did not match the genetic makeup of the HIV that caused Brown's original infection, and debate ensued about whether the fragments actually resulted from lab contamination. And none of the fragments were capable of reproducing (essential for HIV's survival in a host).

The remaining viral particles do raise the question of whether Brown's cure was in fact sterilizing (eradicating all HIV from the body) or functional (cutting the level of virus in the body so low that it can't cause disease, eliminating the need for HIV meds).

Either way, it seems the latest developments in Brown's case provide grounds for more research, but not alarm.