Alliance for Pandemic Preparedness

April 7, 2020

Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients

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  • This experiment compared surgical masks to reusable cloth masks by measuring viral loads after patients coughed while wearing no mask, a surgical mask and a cloth mask. All swabs from the outer mask surfaces were positive for SARS–CoV-2, whereas most swabs from the inner mask surfaces were negative. Neither surgical nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients.
  • Since the size and concentrations of SARS–CoV-2 in aerosols generated during coughing are unknown, more studies are needed to recommend whether face masks decrease transmission of the virus from asymptomatic individuals or those with suspected COVID-19 who are not coughing.

Bae et al. (Apr 6, 2020). Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients. Annals of Internal Med. https://doi.org/10.7326/M20-1342