• William Miller, MD

The Science Behind Wearing Masks - Part 1

Miller Report for the Week of September 7, 2020; by William Miller, MD


There is tremendous scientific support for wearing masks to prevent transmission of all sorts of respiratory infections, not just COVID. Let’s examine some of that evidence and in the process compare different types of masks. The literature can get complicated with discussion of virus particle size, electrostatic charge potentials, etc. However, I think what is most important is to look at studies involving actual infected people and whether the mask prevented transmission.


The strategy for asking everyone to wear masks is to prevent infected people from spreading it to others. Wearing a mask is not to protect the wearer from catching it. This strategy is important because we are trying to minimize the risk of spreading the disease and with time, the disease will fade away. There is also strong evidence that if between 85-100% of all people wore masks consistently, we could probably do away with sheltering in place, restricting businesses and closing down our economy. If you think about it, mask wearing as a strategy is far less costly than people losing jobs and businesses going under. Also, mask wearing has been shown to be more effective than hand washing and social distancing.



It is important for all people to wear masks because people can be contagious before showing any symptoms and many people will never have significant symptoms. Thus, simply saying, “Well, I feel fine so I don’t need a mask on” is wrong. Of all people who get SARS-2 (the virus that causes the disease COVID), about 80% will have no symptoms or minimal symptoms. Only about 20% get really sick and of those, only about a third require hospitalization. When we look at the cases, it appears that at least half of all people get infected got it from someone who never developed symptoms.


Furthermore, we know that the vast majority of infection is from respiratory droplets that we expel when doing things as simple as talking, laughing or singing. These droplets are small globules of saliva that are microscopic and when coming from an infected person are filled with thousands of virus particles. They are then inhaled by others around us, who then become infected. Masks of even the most simple, single layer, cloth construction are very effective in trapping those droplets.

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