The Bible presumes the existence of germs thousands of years before modern science

During the Dark Ages (between 1200 and 1400 AD), the Black Death or Bubonic Plague killed over 1/3 of Europe or 60 million of its 200 million inhabitants.

History records that it was Roman Catholic monks from Vienna who actually stopped the plague’s advance on the mainland continent. The reason for this was because they desperately searched the Bible for answers about how to stop a plague of this magnitude. As a result, they came across, among others, these three passages:

 

"And if any animal which you may eat dies, he who touches its carcass shall be unclean until evening. He who eats of its carcass shall wash his clothes and be unclean until evening. He also who carries its carcass shall wash his clothes and be unclean until evening." Leviticus 11: 40

"Now the leper on whom the sore is, his clothes shall be torn and his head bare; and he shall cover his mustache, and cry, 'Unclean! Unclean!' He shall be unclean. All the days he has the sore he shall be unclean. He is unclean, and he shall dwell alone; his dwelling shall be outside the camp." Leviticus 13: 43 - 46

"This is the law when a man dies in a tent: All who come into the tent and all who are in the tent shall be unclean seven days; and every open vessel, which has no cover fastened on it, is unclean. Whoever in the open field touches one who is slain by a sword or who has died, or a bone of a man, or a grave, shall be unclean seven days." Numbers 19: 14 - 16

As a result of these texts, the monks instituted the first modern quarantine system and thus began the basis for what eventually evolved into our modern hospital system. See Arturo Castiglione, A History of Medicine (pg. 71)

Note that Leviticus 15:13 identifies the importance of bathing in preventing disease (and for ceremonial cleanness) and in particular, bathing in running water.

Importance of proper sanitation is expressed elsewhere in Scripture as well:

 

"Designate a place outside the camp where you can go to relieve yourself. As part of your equipment have something to dig with, and when you relieve yourself, dig a hole and cover up your excrement." Deuteronomy 23: 12 - 13