To mask or not to mask, that is the question. But scientists now think you may want to put a face mask on it after all — if you have one. Their advice is laid out in a new report in Science Magazine. People in Asian countries have been wearing masks for months, which the head of the Chinese Center for Disease and Prevention supports. In the US, face masks are in short supply and government officials want the rapidly dwindling supply saved for health-care professionals. “This virus is transmitted by droplets and close contact. Droplets play a very important...