
I am not a doctor, but I do know a thing or two about mystery ailments, thanks to my many years watching sci-fi and horror movies. Based on this vast knowledge, my guess is that Rodriguez has an alien larva living in his stomach. Either that or he is the first victim of a plague that will soon kill all of humanity except a few select people who divide into good and evil factions, the good living in Colorado and the bad in Las Vegas.
If you see the Trashcan Man, tell him to stay away from the nukes.