Diseases Then Unknown. Diseases were common in the ancient world, but, because medical practitioners of these times described symptoms rather than grouping diseases by classification, and because infectious disease-causing microorganisms alter through mutation, many diseases with which we are afflicted were not known or experienced. Some diseases of this period one cannot identify, probably because the organisms causing them mutated or the human immune system became invulnerable to their infections. Likely the Romans were not affected by smallpox, measles, diphtheria (although this malady was possibly described by Aretaeus of Cappadocia, circa 150-200 C.E., but osteological evidence for it is not found), scarlet fever, and influenza. Neither were they afflicted with the ravaging plagues of pandemic diseases, such as the notorious bubonic plague of 1347 C.E. or syphilis, introduced to Europe in the late fifteenth century. The greatest exception came with a plague...