Nurse Olivia Harper has been at the hospital for a while and is part of the Nurses United Against Mark Sloan group, which implies she and the others have slept with the suave plastic surgeon. Cristina Yang encouraged George to sleep with Olivia because he was in the midst of a dry spell. He did and she gave him Syphillis, which she had acquired from Dr. Alex Karev shortly before she slept with George.