When Dr. Lisa V. Luly-Rivera admitted the 14-year-old girl to the University of Miami’s tent hospital at the airport in Port-au-Prince, the girl’s leg was edematous and she had some hyperpigmentation. But between one day and the next, her leg became warm, and the warmth started moving up toward her thigh. The leg was clearly infected.The surgeons, fearing necrotizing fasciitis, wanted to amputate. Dr. Luly-Rivera, a hospitalist at the University of Miami who was in Haiti to help earthquake...