The Romans did not know about bacteria or what caused diseases such as malaria and dysentery, but they made sure that their soldiers were exposed to fresh, clean air and water, and the military castra were located far away from such sources of “miasmas.”
In the first century B.C., a writer named Varro spoke about the “minute creatures which cannot be seen by the eyes, float through the air, enter the body through the mouth and nose, causing diseases.” Vegetius suggested in the 4th century A.D. that castra must be carefully located away from swamps and that daily exercise does the body “more good than doctors.”
