It sounds like something out of a horror movie, but flesh-eating disease is a very real–and dangerous–thing. The scariest thing about it is that it can happen with the simplest injury involving broken skin, a fact most people aren’t aware of. It happened to 24-year old Aimee Copeland, who had an accident on a homemade zip line last week while on a boating trip with friends in Carollton, Georgia.

After the line snapped and cut her leg, Aimee sought help at a local hospital, where they stitched up the gash on her calf and sent her on her way. But unbeknownst to doctors–and Aimee–a rare type of strep infection had been closed in under her skin, where it burrowed down into the wound and began to deteriorate muscle tissue. When she returned to the hospital the next day complaining of severe pain, doctors gave her a prescription for pain killers, and, later, antibiotics. By Friday, it was clear something else was going on; she was diagnosed with necrotizing fasciitis, which had advanced to a point that necessitated her leg to be amputated up to the hip.

Although it’s not always clear where the infection starts, doctors believe it comes from bacteria housed in the victim’s own body, such as in saliva. It can also survive on the skin, so frequent hand-washing is a must when the skin is broken, even if the cut is small.

Aimee has had some scares since the amputation; doctors lost her pulse this past Tuesday after her fever spiked from the infection. Her father, Andy, said that it was a miracle she survived the amputation at all and that the family could only stay positive in light of the accident. Her friends have taken to Twitter to urge prayers and support.