[Nature] Respiratory virus shedding in exhaled breath and efficacy of face masks

Nature, 3 Apr 2020

Nancy H. L. Leung, Daniel K. W. Chu, Eunice Y. C. Shiu, Kwok-Hung Chan, James J. McDevitt, Benien J. P. Hau, Hui-Ling Yen, Yuguo Li, Dennis K. M. Ip, J. S. Malik Peiris, Wing-Hong Seto, Gabriel M. Leung, Donald K. Milton & Benjamin J. Cowling

Efficacy of surgical face masks in reducing respiratory virus shedding in respiratory droplets and aerosols of symptomatic individuals with coronavirus, influenza virus or rhinovirus infection


  • Surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals.
  • Screened 3,363 individuals in two study phases, ultimately enrolling 246 individuals who provided exhaled breath samples.
  • Aerosol transmission is a potential mode of transmission for coronaviruses as well as influenza viruses and rhinoviruses.
  • Surgical masks can efficaciously reduce the emission of influenza virus particles into the environment in respiratory droplets, but not in aerosols.
  • The majority of participants with influenza virus and coronavirus infection did not shed detectable virus in respiratory droplets or aerosols.
  • There could be considerable heterogeneity in contagiousness of individuals with coronavirus and influenza virus infections.

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