Contagion

There are several passages in the Bible that may not have made much sense at the time, but possibly saved many lives, such as Numbers 5:1-4;

The Lord spoke to Moses, saying: Command the Israelites to put out of the camp everyone who is leprous, or has a discharge, and everyone who is unclean through contact with a corpse; you shall put out both male and female, putting them outside the camp; they must not defile their camp, where I dwell among them.  The Israelites did so, putting them outside the camp; as the Lord had spoken to Moses, so the Israelites did.

 By taking these people out of the camp, any contagious diseases they may have carried were safely removed from the rest of the population.  This helped prevent epidemics that, while not as devastating as those occurring in the Americas when European explorers brought smallpox, would have killed a large percentage of the population.  These people put this law in the Bible as a way to save themselves, and since it is unlikely that they really knew what spread these diseases, perhaps they were significantly more intelligent than most assume in their theory that this would help.

Even now we do something very similar--we call it quarantine.