Galen’s Commentary on Hippocrates’ Epidemics, Book 1

Ed. Chart. IX. [4. 5.]          Ed. Bas. V. (346.)

...[these diseases] are local and distinct, or occur if some universal disease universal: translated from "pangkoinon" (πάγκοινον), referring to a disease that affects an entire population at once should take hold due to the change of the seasons. And again, a little further down: This disease is bred among them both in summer and in winter.

Do not let this point escape you. It was mentioned in the previously written passages and in certain other texts of Hippocrates. Diseases that are always present in a specific region are called endemic endemic: from "endemos," meaning "within the people" or native to a specific place. These are also counted among the diseases common to many people, just like the plague.

For the plague is also one of the common diseases. Hippocrates himself clearly showed this in his book On the Regimen in Acute Diseases original Greek: "peri diaitēs oxeōn" by saying something like this: [5.] When a common type of pestilential disease is not visiting original: "epidēmēsē" (ἐπιδημήσῃ), a verb meaning to stay or visit a place, from which the word "epidemic" is derived, but the diseases are instead sporadic and not similar to one another, more people die from these diseases than from all the others together.

It is clear, therefore, that those within the class of epidemic diseases which are most malignant are called pestilential. The category of epidemic diseases belongs to the class of popular and universal diseases. This class is defined in opposition to sporadic diseases original: "sporades" (σποράδες), meaning scattered or occurring in separate, unrelated cases. This is how Hippocrates himself named them.