What is Ruach Rah

Question

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.)

Answer 1

It's difficult to explain it as simply being bacteria, as the Gemara (Pesachim 112a) clearly says that food under bed gets contaminated with ruach ra'ah even if it was properly sealed.

Interestingly, there is a machlokes as to whether ruach ra'ah even exists nowadays! According to Rambam there are other reasons why you can't place food under bed nowadays. Tosafos (Yuma 77b) and Maharshal (Yam Shel Shlomo, Chulin 8:31) concur. See http://doseofhalacha.blogspot.co.uk/2014/05/food-under-beds.html

Rav Eliezer Melamed explains that it disappeared along with prophecy. It was a mystical evil spirit that shouldn't bother us so much today. http://ph.yhb.org.il/02-08-04/

At times, it means a melancholic, depressive state. Thus, King Saul was struck with this depression (Shmuel I 18:9) upon losing the kingship.

Most often, though, it is understood as a fraction (or akin to) death. Thus, the Beis Yosef (OC 4) writes that ruach ra'ah only descends upon one when they sleep. He compares it to Yaakov's struggle with the angel, and explains the connection with death. This is why one can't take food into a cemetery, etc. either. (See Rambam, Hilchos Rotzeach 12:5). It is for this reason that we wash our hands after leaving a cemetery, too.

Answer 2

Rabbi Ahron Soloveichik explained to me that "Ruach Rah" is referring to things like bacteria and germs.

Our Chachamim, Sages, were very advanced thinkers. They must have seen certain cause and effect. If you don't wash your hands disease etc is transferred. They obviously did not have a microscope to see the bacteria or germs, however they identified a physical cause to the harm. They referred to this as Ruach Rah.