Right in the beginning of Shulchan Aruch we see this idea of "Ruach Rah". In regards to washing ones hands and all that comes before that -- not walking more than 4 amos without washing one's hands, not touching orifices of the body without washing ones hands. All done in order not to cause a danger to someone. Is there any explanation that can be given to understand better what Ruach Rah is, where it comes from. What sources could be quoted about this.
My reason for asking this is because I am learning with someone now for a half hour a day and he would like a better explanation in this inyun of Ruach Rah (like I stated above, where it comes from, why, how does it "work", etc.)