Is 'pathocoenosis', a notion conceived and a word coined by Mirko Grmek (1969), useful as far as ancient history is concerned? The author is interested in Galenic pathocoenosis, that of doctor Galen and his Emperor Marcus Aurelius (IInd cent. A.D.), when a new 'pestilence' or 'plague' (smallpox?) devastated the whole empire, from Mesopotamia to the Danube at least.