Okay, back to where I left off. I am feeling so rusty and going to have to backtrack somewhat. Leviticus 13:4 is basically saying if a bright white spot is not deeper than the skin and the hair has not turned white, then the person who has the symptom needs to held in isolation for seven days. The Bible doesn't really explain that others can catch leprosy if they are exposed to someone with it, but it's interesting that despite Moses not really knowing too much about diseases back then that God will command what would happen to patients anyway in these times.
In a way, maintaining sanitary conditions and separating patients with others so they don't catch a deadly disease seems like a little advanced knowledge for back then, when there's really no evidence for sophisticated medical discoveries. Don't you think?