There was a video posted here several days ago with a youtuber (Asian Boss I think) who interviewed a top South Korean expert on the virus. Apparently, just about everybody in Korea wears a mask out in public at this time. He was asked if masks were effective and he said something like, "Of course they work. Why would hospital workers wear them if they didn't work?"

He also said he thought it was strange that Americans and Europeans don't wear masks.