It is only when disease manifests as illness that we see it as unnatural, in the “contrary to the ordinary course of nature” sense of the word. When a child’s fingers blacken on his hand from Hib disease, when tetanus locks a child’s jaw and stiffens her body, when a baby barks for breath from pertussis, when a child’s legs are twisted and shrunken with polio—then disease does not seem natural.
