Sierra Jane Downing is alive and well despite contracting an illness that wiped out a big chunk of Europe's population more than 600 years ago. The seven-year-old girl from Colorado was infected with bubonic plague after trying to bury a dead squirrel during a camping trip - against her mother's instructions. (SOUNDBITE) (English) DARCY DOWNING MOTHER OF SICK CHILD: "Sierra Jane had found a squirrel and she was very concerned about it. She just really wanted to bury it. It was partially eaten; an animal had gotten a hold of it and so, she was over there, and we redirected her and told her to stay away from it." Although the bubonic plague once killed between 30 and 60 percent of Europe's population, these days in the US there are only a handful of cases per year. The illness can now be easily treated -- as long as it's diagnosed in time. And this is exactly what happened with Sierra - who is expected to make a full recovery - but her doctors said it was a close call. (SOUNDBITE) (English) JENIFER SNOW, PEDIATRICIAN: "We were pretty close, I did tell the parents that I'm always hopeful that everything is going to turn out for the best, but I was trying to prepare them somewhat that she was critically ill and this is a life-threatening condition that she had and we were doing absolutely everything we could to save her life."