This is a surprisingly complicated question. The answer depends on quite a few things.
By now you have likely heard the Centers for Disease Control recommendation for the public to wear face covering, whether it be a scarf, bandana, cloth mask or medical mask. Before you decide to wear a mask, these are things you should consider.
1. Masks are much more likely to prevent people getting infected from you than you getting infected from other people. Even cloth masks work well to catch the infectious droplets that come out of your mouth. Loose fitting medical masks have only limited ability to prevent infectious droplets from getting into your respiratory tract, but they still catch your droplets well. Since it is known that people who have the virus but do not yet have symptoms can transmit the virus to others, it is a reasonable strategy to wear a mask in public. But the benefit is limited unless (nearly) everybody wears a mask. Think of it like this: Masks don’t protect each of us, they protect all of us.
2. If you decide to wear a mask, make sure it securely covers both your mouth and nose. If either your mouth or nose are left uncovered, then the mask will provide no benefit either to you or to others in your vicinity.
3. If you work in a health care setting, you should strongly consider wearing a mask at all times while at work. Since the virus is more likely to be present in health care settings, the benefit of universal masking in that environment is much greater than in the general public. We also know, unfortunately, that health care workers are more likely to become infected than those who do not work in health care. Therefore wearing masks in the hospital or doctor’s office can help to prevent infected health care workers who don’t yet have symptoms from spreading the virus to others.
4. If you have symptoms from the virus, you should wear a mask in your home if you live with others. This will help to prevent shedding of virus to others in your household. (You should also quarantine yourself as best as possible in your home). If you have any symptoms from the virus you still should not be venturing out with or without a mask! People with symptoms are much more contagious than people without symptoms, so the best place to leave the virus is in your home. Also liberally disinfect surfaces in your home; this will help to prevent others in your home from becoming infected by touching infected droplets on surfaces and then touching their eyes, nose or mouth.
5. N95 respirators are masks that are tight fitting and can filter out the virus effectively. Additionally they must be fit-tested to ensure protection. N95s may provide very little protection for you or others if you have facial hair or you are not properly fit-tested. Since the nationwide supply of N95s is critically short, health care workers must have priority access to these masks. If you find yourself with a supply of N95s, consider donating them to your local hospital and replacing them with cloth masks.
6. One of the biggest concerns about wearing masks is that it may give people who wear them a false sense of security. Wearing a mask is not a substitute for self-quarantine, social distancing or frequent hand washing as it is still possible to contract the virus while wearing a mask.
7. If you are immunocompromised, you may have already been instructed by your physician to wear a mask at all times when in public. You should continue to do this when you have to go out, but a much safer strategy is to stay in your home for all but essential trips outside.
Stay safe and please keep health care workers in your thoughts.