While luring several Rabids away so that Dean and Jenna Nickerson could escape with Amara, Sam hid in the supply closet the nurse was trapped in, not realizing that she was in there until too late. The nurse attacked Sam and the two fought, culminating in the nurse grabbing a dropped scalpel to stab Sam with. Sam managed to turn the scalpel on the nurse, slitting her throat and killing her but splashing his face and mouth with her blood. Moments later, three Rabids broke into the supply closet, but after sniffing Sam, unexpectedly left.
As Sam talked to Dean on the phone, the nurse's corpse remained near his feet. After getting off of the phone, Sam checked himself in the mirror and discovered that getting splashed with the nurse's blood had infected Sam with the Rabid infection as well.