Effectiveness of Face Masks in Preventing Airborne Transmission of SARS-CoV-2

Abstract

Guidelines from the CDC and the WHO recommend the wearing of face masks to prevent the spread of coronavirus (CoV) disease 2019 (COVID-19); however, the protective efficiency of such masks against airborne transmission of infectious severe acute respiratory syndrome CoV-2 (SARS-CoV-2) droplets/aerosols is unknown. Here, we developed an airborne transmission simulator of infectious SARS-CoV-2-containing droplets/aerosols produced by human respiration and coughs and assessed the transmissibility of the infectious droplets/aerosols and the ability of various types of face masks to block the transmission. We found that cotton masks, surgical masks, and N95 masks all have a protective effect with respect to the transmission of infective droplets/aerosols of SARS-CoV-2 and that the protective efficiency was higher when masks were worn by a virus spreader. Importantly, medical masks (surgical masks and even N95 masks) were not able to completely block the transmission of virus droplets/aerosols even when completely sealed. Our data will help medical workers understand the proper use and performance of masks and determine whether they need additional equipment to protect themselves from infected patients. IMPORTANCE Airborne simulation experiments showed that cotton masks, surgical masks, and N95 masks provide some protection from the transmission of infective SARS-CoV-2 droplets/aerosols; however, medical masks (surgical masks and even N95 masks) could not completely block the transmission of virus droplets/aerosols even when sealed.

Is a COVID-19 Vaccine Likely to Make Things Worse?

“…The N95 mask has the highest protective efficacy: approximately 80–90% reduction in virus intake. In contrast, cotton and surgical masks blocked more than 50% of the virus outward transmission, whereas the N95 masks showed approximately 90% protective efficacy [ 31 ]. The average filtration efficiency of single-layer fabrics and of layered combination was found to be 35% and 45%, respectively [ 32 ].…”

Uniting Infectious Disease and Physical Science Principles on the Importance of Face Masks for COVID-19

“…The masks were 60%–70% effective at protecting others and 50% effective at protecting the wearer. 10 The mechanism by which masks block viruses depends purely on the physical characteristics of the carrier droplet or aerosol and not the virus itself, so evidence for other viruses can be extended to SARS-COV-2 with careful consideration of the size of the droplets and aerosols involved. For instance, in a study of patients with documented infections with either seasonal coronaviruses or influenza virus, surgical masks blocked coronaviruses released into the air to undetectable levels and partially blocked influenza virus.…”

Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk

“…They found that three double-layers of any tested fabric could meet the pressure difference standards and particle filtration efficiency of graded masks. More recently, Ueki et al [4] tested two manikin heads in a biosafety level 3 box, exhaling droplets that were originally…”