If you do not have any respiratory symptoms, such as fever, cough, or runny nose, you do not need to wear a medical mask. When used alone, masks can give you a false feeling of protection and can even be a source of infection when not used correctly. 
https://bit.ly/2QN3QOp pic.twitter.com/JDQhnowx3p
They've been saying this shit since SARS 1. I distinctly remember hearing about why the Chinese were just being silly wearing all those masks