The disease the transforms a normal Human into a Furry. Furryitis is contacted via the Internets, but is most common on 4Chan or 7Chan. Furryitis is caused by a parasitic microorganism known as a proto-Furry that enters the brain through the corneas when the victim sees to many Furry drawings or forum posts and converts them into a Furry. The only known cure for Furryitis is Shotgun Therapy.
Joey: "Doctor, I was reading some forum posts last night and now I have a strange desire to have sex dressed up like a fox."
Doctor: "Joey, I'm afraid you have Furryitis"
Joey: "Can you fix it?"
Doctor: "Yes, hold still" *Reaches under desk for shotgun*