How effective are face masks in preventing transmission of coronaviruses from symptomatic individuals?

Bottom Line:

Surgical masks can reduce the emission of coronavirus in large respiratory droplets and in aerosols.

Reference:

Leung, N.H.L. et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nature Medicine (2020). https://doi.org/10.1038/s41591-020-0843-2

Date Published:

3 April 2020

Synopsis:

The researchers identified aerosol transmission as a potential mode of transmission for coronarviruses, in addition to already identified droplet transmission. They also found that a majority of patients did not shed detectable virus in respiratory droplets or aerosols and among those who did, viral load was relatively low. This result suggests that prolonged close contact may be required for transmission to occur and that there could be heterogeneity in contagiousness. Finally, the authors found that surgical masks worn by the patient, as a method of source control, can reduce the emission of coronavirus in large respiratory droplets and in aerosols. Taken together, these findings may help guide public health and hospital PPE guidelines in the COVID-19 and any possible future pandemics.

Summary by: Mike Ge