Forcing everyone to wear masks will matter very little unless asymptomatic people spread the coronavirus in large numbers. Everyone agrees people who are symptomatic with a fever or cough should stay home or wear a mask if they must go out. If only sick people are wearing masks, face coverings may function as a public signal: I don’t feel well, stay away. But the point of universal mask mandates is to force people who do not feel sick to wear masks anyway, on the theory that people without symptoms can also spread the virus.
