Filtration efficiency of face masks against aerosolized surrogate SARS-CoV-2 at different social distances

The coronavirus disease 2019(COVID-19)pandemic is an unpreedented global event.It has become clear that COVID-19 is transmitted by virus-containing droplets(＞5 μm)and aerosols(＜5 μm),and that all human exhalatory activities(e.g.,breathing,speaking,singing,shouting,coughing,and sneezing)result in the emission of suspended droplets/aerosols of various sizes.As an example,COVID-19 patients exhale millions of severe acute respi-ratory syndrome coronavirus 2(SARS-CoV-2)RNA copies into the air per hour[1].SARS-CoV-2-laden aerosols play a profound role in disease transmission,as they can linger and remain viable in the air for a long duration(～16 h)[2]and travel a long distance(～4.8 m)due to their smaller size[3].