Study shows pandemic could end – face masks lower the ERN

Chris Burns - Nov 24, 2020, 12:28pm CST
Study shows pandemic could end – face masks lower the ERN

A study conducted this year using COVID-19 outbreak and containment data showed that consistent use of facemasks could potentially end the pandemic. The study’s focus was fluid flow behavior of respiratory droplets and aerosols through facemasks with a special focus on SARS-CoV-2 and COVID-19.

The key metric

Research published this week listed and expanded on what we know about face mask wear and prevention of spread of respiratory infections among the public. They key is the effective reproduction number (ERN).

If the ERN is above 1, each human with COVID-19 can be expected to infect at least one other person, and possibly more. If the number is below 1, we expect that there’s a chance each human with COVID-19 will avoid infecting another human. If the ERN is below 1, and starts to move downward, we’re heading in the right direction.

NOTE: The imagery and video included in this article is credited to Heow Pueh Lee, and the research linked at the end of this post.

The mask math

A study was published in July of 2020 called Mathematical assessment of the impact of non-pharmaceutical interventions on curtailing the 2019 novel Coronavirus. This study was authored by Calistus N. Ngonghala et. al, and can be found with code DOI:10.1016/j.mbs.2020.108364. This study suggested that “high use of face-masks in public could lead to COVID-19 elimination.”

This same study suggested that “The use of efficacious face-masks (such as surgical masks, with estimated efficacy 70%) in public could lead to the elimination of the pandemic if at least 70% of the residents of New York state use such masks in public consistently (nationwide, a compliance of at least 80% will be required using such masks).”

They also noted that the use of less effective masks could lead to “significant reduction of COVID-19 burden” but would not, ultimately, lead to elimination. Less effective masks referenced here point to those masks with an estimated efficacy less than 30%.

The study published this week by Kumar and Lee showed tests with household materials “do not provide much protection against the virus transmission via droplets and, therefore, are unsuitable as materials for protective masks.” They went on to list filtering facepiece respirator (FFR) performance-based masks that offer adequate protection:

FFR masks listed as suitable for droplet filtration:
• FFP2 (Europe EN 149-2001)
• N95 (United States NIOSH-42CFR84)
• DS2 (Japan JMHLW-Notification 214, 2018)
• KN95 (China GB2626-2006)

More masks, better masks

The aim with this latest research was “a theoretical investigation of fluid flow mechanisms involved in the virus-laden particles’ prevention by using facemasks.” Researchers Sanjay Kumar and Heow Pueh Lee hope that their work can contribute to more effective mask designs and products in the future. Design aspects like thermal comfort and flow resistance are vital to design effectiveness and likelihood of human use as we continue to fight COVID-19.

You can learn more about this study in the paper The perspective of fluid flow behavior of respiratory droplets and aerosols through the facemasks in context of SARS-CoV-2 as authored by Sanjay Kumar and Heow Pueh Lee. This paper can be found with code DOI:10.1063/5.0029767 in the scientific research publication Physics of Fluids as of November 24, 2020.


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