Dean Winchester: All right, so what do we know? Um, if you kiss someone, and then they die?
Sam Winchester: I guess. Wait a second. You didn't kiss Staci.
Melissa Harper: No, of course not.
Dean Winchester: No, but Dan did.
Sam Winchester: So the curse is transmittable?
Dean Winchester: Like a magic STD. Okay, that works. Kind of makes you nostalgic for good, old-fashioned herpes.