What disabilities preclude wearing masks? - PTSD (combat veterans, survivors of abuse, rape, kidnapping, etc.) or other mental health issues, facial injuries/d

What disabilities preclude wearing masks? - PTSD (combat veterans, survivors of abuse, rape, kidnapping, etc.) or other mental health issues, facial injuries/deformities, lung conditions. How does one know that they don't have Covid? - Testing; recovering from the virus and passing a test. Do we know for sure that someone who previously had Covid cannot become a spreader again? - Not much data here that I've found, of course, since it is rare and new. One could be overly cautious because it is "novel" and assume that a healthy immune system could allow reinfection fairly quickly as there have been a few documented reinfections, or look at other coronaviruses (MERS/SARS) and assume that is more likely to take months to years to become infectious, after being infected again.