In March 2009, MRSA made headlines in Tennessee when Kristen, a healthy 11-year-old girl, became infected.

One day, Amanda, Kristen's mom, says her daughter came home from school with an extremely sore throat. Her dad, Scott, took her to see a doctor. "They said it was a virus," Amanda says. "A lot of things were going around in school, and they sent her home with a strong antibiotic."

Watch Kristen's family tell her story. 

Two days later, Kristen's health began to deteriorate. She had trouble breathing and complained of severe back pain. Doctors X-rayed her lungs and then rushed her to the pediatric intensive care unit at a nearby hospital. MRSA had invaded and ravaged Kristen's lungs, leaving her in critical condition.