dis·ease A disorder of structure or function in a human, animal, or plant, especially one that produces specific signs or symptoms or that affects a specific location and is not simply a direct result of physical injury.  literally they are diseased.  Thankfully our disgust reaction will also keep most people from mating with the hideous creatures so they can't spread their habits to offspring. Honestly, having some massive global trauma would be good. It might be hard to survive, but at least it'd bring about the extinction of obeasts.