SARS-CoV-2 has a diameter between 0.06 and 0.14 microns.19 Medical N95 masks — which are considered the most effective — can filter particles as small as 0.3 microns.20 Surgical masks, homemade masks, T-shirts and bandanas are even more porous. Similarly, a May 2020 policy review paper23 published in the Centers for Disease Control and Prevention’s journal, Emerging Infectious Diseases, concluded that “Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.” This is highly relevant, as the influenza virus is about twice the size of SARS-CoV-2. If masks cannot prevent transmission of influenza, they certainly cannot prevent transmission of SARS-CoV-2.
