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 syndrome CoV-2 (SARS-CoV-2) droplets/aerosols
is unknown.However, infectious virus penetration was measurable even when the N95 mask
was completely fitted to the face with adhesive tape"Importantly, medical masks (surgical masks and even N95 masks)
were not able to completely block the transmission of virus droplets/aerosols
even when fully sealed under the conditions that we tested.
These results indicate that
it is difficult to completely block this virus even with a properly fitted N95 mask. However, it
remains unknown whether the small amount of virus that was able to pass through the N95 masks
would result in illness.
Viral RNA was detected in all samples
It has been reported that the stability of the virus in the air changes depending on the droplet/aerosol components, such as inorganics, proteins, and surfactants, suggesting that
the permeation efficiency of masks is also affected by the components of viral droplets/aerosols (
5,
6). In our experiments, the virus was suspended in culture supernatant without fetal calf serum or was diluted with phosphate-buffered saline. Further detailed analysis will be required to reveal the precise relationship between the protective efficiency of masks and the components of viral droplets/aerosols.