I havent worn a mask yet, not concerned, not sick. If you are sick, they don't stop the virus coming in or out unless they are in droplets 3 microns or larger. The virus lives longer in droplet form. The individual virus is smaller than the ability of the mask to filter it, but a mask will capture virus contained in droplets, so if someone is actually sick with sneezing and coughing, they should wear a mask to reduce or eliminate spewing droplets. Most won't get sick, or will have mild symptoms. There is really no reason to wear a mask unless you are sick, coughing and sneezing ... as a courtesy to others. Or a first responder or people fearful of catching it due to their preexisting health issues, though wearing a mask offers little protection with O2 depletion.