a potential donor dies. joshua gets one of the man's kidneys and then suddenly, instead of getting better, he gets sicker. >> he was throwing up, headaches, had the shakes real bad. sleeping a lot. >> within months joshua is dead, at age 18. a doctor tells his mother he died of rabies. >> and i said, what do you mean rabies? like some foreign branch of rabies? or some kind that is, you know, uncommon or rare? and i said or the kind that you vaccinate your dog every year for? and he said, jennifer, the kind you vaccinate your dog every year for. >> and just how does this teenager get rabies, a virus that's spread by animals? that new kidney he gets is infected with rabies before it even gets inside his body. here's what happened. the organ donor has been bitten by a bat, but no one knows it. the virus spreads through the bloodstream. >> no one suspected that this person had rabies.