Even if the masks did help to prevent the transmission of the virus, the effect of lowering oxygen levels could interfere with brain function. I’d want my surgeon to be able to think clearly while he was operating on me! Also, I know from experience lower levels of oxygen can cause the inability to move as well or as quickly as one would otherwise be able to. I agree, we need to take our chances (even the at-risk, one of which I am) to get this thing under control.