Peregrine Horden (1992)
Disease, dragons and saints: the management of epidemics in the Dark Ages
In: Epidemics and Ideas: Essays on the Historical Perception of Pestilence, ed. by Terence Ranger and Paul Slack. Cambridge University Press, Cambridge, pp. 45-76.
The article suggests that dragons were concrete embodiments of water-borne disease in the minds of the population, and might often represent real animals (e.g. snakes), exaggerated by fear. The often recorded miraculous control of epidemics by dragon-slaying saints makes good sense in this context.