The Disease of Immoral Behavior
Throughout antiquity, most people assumed that illness was a punishment from the gods. Incensed at some infraction of ritual law, pagan gods were forever visiting terrible diseases, sometimes to the point of death, on their worshipers.
In fact, this tendency to attribute divine disfavor to any manifestation of sickness runs rampant in our society as well (although only for the illness of someone else!).