• About Us
    • Contact Us
    • Login
    • ObGFirst
  • COVID-19
  • Alerts
  • OB
  • 2T US Atlas
  • The Genome
  • GYN
    • GYN
    • Sexual Health
  • Primary Care
  • Your Practice
  • #GrandRounds
  • My Bookshelf
  • Now@ObG
  • Media
About Us Contact Us Login ObGFirst
  • COVID-19
  • Alerts
  • OB
  • 2T US Atlas
  • The Genome
  • GYN
    • 0 CME Hours
    • GYN
    • Sexual Health
  • Primary Care
  • Your Practice
  • #GrandRounds
  • My Bookshelf
  • Now@ObG
  • Media
COVID-19 Testing

Surgical Masks Reduce Viral Shedding

image_pdfFavoriteLoadingFavorite

BACKGROUND AND PURPOSE:

  • Leung et al. (Nature Medicine, 2020) investigated aerosol routes of transmission to determine the potential efficacy of surgical masks to prevent respiratory virus transmission

METHODS:

  • Randomized controlled trial (2013 to 2016)
  • Participants
    • Patients with viral symptoms were eligible to participate if they were within 3 days of illness onset and ≥11 years of age
  • Interventions
    • Wearing a face mask
    • Not wearing a face mask
  • Study design
    • Told to breathe normally | Natural coughing allowed | Conducted for 30 minutes
    • Second sample crossover sample requested (no mask to masked and vice versa) | Most participants did not provide second breath exhalation due to time constraints | 20% (n=49) provided a second sample
    • Nasal and throat swabs collected and analyzed
    • Infections confirmed by reverse transcription PCR (RT–PCR)
      • Human (seasonal) coronavirus (not SARS-CoV-2)
      • Influenza virus
      • Rhinovirus
    • Exhaled breath particles collected and differentiated into 2 size fractions
      • Course fraction (respiratory droplets): Particle aerodynamic diameter >5 μm
      • Fine fraction (aerosols): Particle aerodynamic diatmeter ≤5 μm
  • Primary outcome
    • Efficacy of face masks in preventing virus dissemination in exhaled breath
    • Respiratory droplets and aerosols considered separately
  • Secondary outcomes
    • Correlation between viral shedding in nose swabs, throat swabs, respiratory droplets and aerosols
    • Factors affecting viral shedding in respiratory droplets and aerosols

RESULTS:

  • A total of 246 participants provided breath samples
    • Not wearing a mask: 122
    • Wearing a mask: 124
  • Infection with a respiratory virus was confirmed in 123 (50%) of patients, and 111 patients (90%) had at least one of the following
    • Human (seasonal) coronavirus: 17
    • Influenza virus: 43
    • Rhinovirus: 54
  • Viral shedding was higher in those with positive nasal swabs than in throat swabs

No Mask Group

  • Viral RNA was identified from respiratory droplets and aerosols for all three viruses while not wearing a face mask
    • Human (seasonal) coronavirus
      • Respiratory droplets: 30%
      • Aerosols: 40%
    • Influenza virus
      • Respiratory droplets: 26%
      • Aerosols: 35%
    • Rhinovirus
      • Respiratory droplets: 28%
      • Aerosols: 56%

Mask Group

  • Coronavirus
    • There was no coronavirus viral RNA detected in respiratory droplets or aerosols collected from participants wearing face masks
    • Significant reduction by wearing face masks in detection of coronavirus in aerosols (P=0.04)
    • Trend towards reduction in detection in respiratory droplets (P=0.09)
  • Influenza
    • Significant reduction in the facemask group in detection of influenza virus in respiratory droplets (P=0.04)
    • No difference was found in aerosols (P=0.36)
  • Rhinovirus
    • No significant differences found for either respiratory droplets or aerosols

CONCLUSION:

  • Even without masks, majority of patients did not shed virus and those who did, the viral load was relatively low
    • Suggests close contact for longer time frame may be required to transmit these viruses
    • This study evaluated breathing, not coughing
  • This study found evidence for aerosol transmission of coronaviruses, influenza, and rhinoviruses
    • If SARS-CoV-2 is similar to other coronaviruses studied here, spread could happen through aerosols
    • The authors suggest that transmission of COVID-19 could be reduced by symptomatic individuals wearing surgical masks

Learn More – Primary Sources:

Respiratory virus shedding in exhaled breath and efficacy of face masks

Get COVID-19 Research Summaries Direct to Your Phone, with ObGFirst

Try it Free »

image_pdfFavoriteLoadingFavorite
< Previous
All COVID-19 Testing Posts
Next >

Related ObG Topics:

Aerosols and Surfaces: SARS-CoV-2 Stability
COVID-19 Guidance: Key Highlights for Healthcare Professionals
CDC Weekly Update: Which Comorbidities are Associated with COVID-19 in the US?

Sections

  • COVID-19
  • Alerts
  • OB
  • GYN
    • GYN
    • Sexual Health
  • 2T US Atlas
  • The Genome
  • Primary Care
  • Your Practice
  • #Grand Rounds
  • My Bookshelf
  • Now@ObG
  • Media

ObG Library

  • Hysteroscopy
  • Fertility
  • Site Map/
  • © ObG Project/
  • Terms and Conditions/
  • Privacy/
  • Contact Us/
© ObG Project
SSL Certificate


  • Already an ObGFirst Member?
    Welcome back

    Log In

    Want to sign up?
    Get guideline notifications
    CME Included

    Sign Up

Get Guideline Alerts Direct to Your Phone
Try ObGFirst Free!

Sign In

Lost your password?

Sign Up for ObGFirst and Stay Ahead

  • - Professional guideline notifications
  • - Daily summary of a clinically relevant
    research paper
  • - Includes 1 hour of CME every month

ObGFirst Free Trial

Log In to ObG First

Please log in to access OBGFirst and the 2T Ultrasound Atlas

Password Trouble?

Sign Up for ObGFirst

  • - Access 2T US Atlas
  • - Guideline notifications
  • - Daily research paper summaries
  • - And lots more!

ObG First Free Trial

Media - Internet

Computer System Requirements

OBG Project CME requires a modern web browser (Internet Explorer 10+, Mozilla Firefox, Apple Safari, Google Chrome, Microsoft Edge). Certain educational activities may require additional software to view multimedia, presentation, or printable versions of their content. These activities will be marked as such and will provide links to the required software. That software may be: Adobe Flash, Apple QuickTime, Adobe Acrobat, Microsoft PowerPoint, Windows Media Player, or Real Networks Real One Player.

Disclosure of Unlabeled Use

This educational activity may contain discussion of published and/or investigational uses of agents that are not indicated by the FDA. The planners of this activity do not recommend the use of any agent outside of the labeled indications.

The opinions expressed in the educational activity are those of the faculty and do not necessarily represent the views of the planners. Please refer to the official prescribing information for each product for discussion of approved indications, contraindications, and warnings.

Disclaimer

Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information
presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patient’s conditions and possible contraindications and/or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.

Jointly provided by

NOT ENOUGH CME HOURS

It appears you don't have enough CME Hours to take this Post-Test. Feel free to buy additional CME hours or upgrade your current CME subscription plan

Subscribe

JOIN OBGFIRST AND GET CME/CE CREDITS

One of the benefits of an ObGFirst subscription is the ability to earn CME/CE credits from the ObG entries you read. Tap the button to learn more about ObGFirst

Learn More
Leaving ObG Website

You are now leaving the ObG website and on your way to PRIORITY at UCSF, an independent website. Therefore, we are not responsible for the content or availability of this site