Effectiveness of Surgical Masks in Reducing Viral Shedding in Exhaled Breath

A detailed study published in Nature Medicine provides valuable insights into the effectiveness of surgical face masks in reducing viral shedding of respiratory viruses in exhaled breath.

Here’s a summary:

  1. Study Overview: The study focused on the shedding of seasonal human coronaviruses, influenza viruses, and rhinoviruses in exhaled breath and coughs of individuals with acute respiratory illness. It involved screening 3,363 individuals, with 246 providing exhaled breath samples. Half of the participants were randomized to not wearing a face mask, and the other half were wearing a face mask during the first exhaled breath collection.
  2. Key Findings: The study found that surgical face masks significantly reduced the detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols. This suggests that face masks could be effective in preventing the transmission of these viruses from symptomatic individuals.
  3. Viral Shedding Analysis: Viral shedding was analyzed in nasal swabs, throat swabs, respiratory droplet samples, and aerosol samples. On average, higher viral shedding was observed in nasal swabs compared to throat swabs for coronavirus, influenza, and rhinovirus. The presence of viral RNA was identified in 30%, 26%, and 28% of respiratory droplets and 40%, 35%, and 56% of aerosols collected without a face mask for coronavirus, influenza, and rhinovirus, respectively.
  4. Implications for Aerosol Transmission: The study indicates that aerosol transmission is a potential mode of transmission for these viruses. While surgical masks were shown to reduce the emission of influenza virus particles into the environment effectively, their impact on aerosols was less clear. The majority of participants with influenza virus and coronavirus infection did not shed detectable virus in respiratory droplets or aerosols without a face mask, whereas for rhinovirus, virus detection was higher in aerosols.
  5. Conclusion: The research suggests that surgical face masks can reduce the transmission of human coronaviruses and influenza viruses, particularly in respiratory droplets. This finding is significant for controlling the spread of respiratory viruses, including in the context of the COVID-19 pandemic. The study underscores the importance of using face masks, especially by ill individuals, to reduce onward transmission.

This study provides compelling evidence supporting the use of surgical masks in reducing the transmission of respiratory viruses, highlighting their role as a simple yet effective tool in public health strategies​​​​.

Read More: https://www.nature.com/articles/s41591-020-0843-2

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