Res Gestae

And, as Thucydides shows,[*](Cf. Thuc. ii. 4, 7.) that calamity which, at the beginning of the Peloponnesian war, harassed the Athenians with a grievous kind of sickness, gradually crept

Others believe that when the air, as often happens, and the waters are polluted by the stench of corpses or the like, the greater part of their healthfulness is spoiled, or at any rate that a sudden change of air causes minor ailments.

Some also assert that when the air is made heavy by grosser exhalations from the earth, it checks the secretions that should be expelled from the body, and is fatal to some; and it is for that reason, as we know on the authority of Homer[*](Iliad, i. 50, οὐρῆας μὲν πρῶτον ἐπῴχετο καὶ κύνας ἀργούς.) as well as from many later experiences, that when such a pestilence has appeared, the other animals besides man, which constantly look downward, are the first to perish.

Now the first kind of plague is called endemic, and causes those who live in places that are too dry to be cut off by frequent fevers. The second is epidemic, which breaks out at certain seasons of the year, dimming the sight of the eyes and causing a dangerous flow of moisture. The third is loemodes,[*](Pestilential.) which is also periodic, but deadly from its winged speed.