- Aerosol is a potential mode of transmission from asymptomatic individuals.
- Surgical masks could reduce the emission of virus particles into the environment in droplets and aerosols. Therefore, they have the potential to reduce onward transmission if worn by symptomatic individuals.
- Only a minority (35%) of infected participants shed detectable virus in droplets or aerosols, and the viral load tended to be low. Therefore, prolonged close contact would be required for these routes of transmission to occur.
- However, in those who shed virus, there is no evidence of declines in viral shedding by time since onset of viral illness.
This data comes from an analysis of 246 participants, 122 of participants were randomized to not wear a face mask and 124 participants were randomized to wear a face mask. Coronavirus were tested positive in 17 participants. In the group without face masks, coronavirus were detected in 30% of droplets samples and 40% of aerosols samples. In the group with face masks, coronavirus were not detected in any of the droplets or aerosols samples (0%). Viral shedding was also reduced in the group with face masks for both droplets and aerosols.
- Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al. (April 03, 2020). Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med.