Efficacy of Face Masks

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Salient Points

This article reports a randomised study on  the shedding of respiratory viruses including seasonal influenza and seasonal corona viruses in exhaled breath and the efficacy of face masks in preventing their transmission.

Coronavirus was detected in respiratory droplets and aerosols in 3 of 10 and 4 of 10 of the samples collected without face masks.No virus was detected in respiratory droplets and aerosols collected from participants wearing face masks, suggesting that face masks are effective in preventing the transmission of human coronavirus and influenza viruses from symptomatic individuals.

Detailed Summary

These viruses spread between humans through direct or indirect contact, respiratory droplets (including larger droplets that fall rapidly near the source as well as coarse aerosols with aerodynamic diameter >5 µm) and fine-particle aerosols (droplets and droplet nuclei with aerodynamic diameter ≤5 µm)

The study was conducted among 3,363 individuals, enrolling 246 individuals who provided exhaled breath samples.

Among the 246 individuals:

  • 50% were randomised to not wearing a face mask during their exhaled breath collection
  • 50% were randomised to wearing a face mask during the same.

Results

  • Infections of at least one respiratory virus was confirmed by reverse transcription PCR (RT-PCR) in 123 of 245 (50%) participants.
  • Of these 123 participants, 111 (90%) were infected by human (seasonal) coronavirus, influenza virus or rhinovirus
  • One participant had a co-infection of both coronavirus and influenza virus.
  • Out of the 111 participants above:
  1. 24% had measured a fever >= 37.8 °C
  • Coronavirus infected participants coughed the most with an average of 17 coughs over the 30 min duration of exhaled breath collection.
  • Viral shedding was highest in Nasal Swabs.
  • Viral RNA was identified from respiratory droplets and aerosols for all three viruses, being 30%, 26% and 28% of respiratory droplets and 40%, 35% and 56% of aerosols collected while not wearing a face mask, from coronavirus, influenza virus and rhinovirus-infected participants, respectively.
  • For coronavirus, OC43 and HKU1 were identified from both respiratory droplets and aerosols, but only identified NL63 from aerosols and not respiratory droplets.

Coronavirus was detected in respiratory droplets and aerosols in 3 out of 10 and 4 out of 10 of the samples collected without face masks. But No virus was detected in respiratory droplets and aerosols collected from participants wearing face masks.

Reference Link : https://www.nature.com/articles/s41591-020-0843-2

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