National Center For Biotechnology Information
“However, absence of proof of an effect is not the same as proof of absence of an effect. During the pandemics caused by swine flu and by the coronaviruses which caused SARS and MERS, many people in Asia and elsewhere walked around wearing surgical or homemade cotton masks to protect themselves. One danger of doing this is the illusion of protection. Surgical facemasks are designed to be discarded after single use. As they become moist they become porous and no longer protect. Indeed, experiments have shown that surgical and cotton masks do not trap the SARS‐CoV‐2 (COVID‐19) virus, which can be detected on the outer surface of the masks for up to 7 days. 7 , 8 Thus, a pre‐symptomatic or mildly infected person wearing a facemask for hours without changing it and without washing hands every time they touched the mask could paradoxically increase the risk of infecting others.”