Plenty of Science to Support Masks to Slow the Spread of COVID 19

Plenty of Science to Support Masks to Slow the Spread of COVID 19

The purpose of this article is to demonstrate the science behind the wisdom of the recommendation to wear cloth face coverings or other appropriate masks when social distancing is not possible during a pandemic like COVID 19 where the disease is spread through respiratory droplets.

The wisdom is derived from two main concepts; 1. Asymptomatic and pre-symptomatic spread are significant sources of spread of COVID 19 and; 2. Cloth face masks safely provide a significant level of protection from respiratory droplets thereby reducing the spread. 


Asymptomatic Spread; Viral Load; Contact Tracing

  • Rothe C, Schunk M, Sothmann P, et al. Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany. The New England journal of medicine. 2020;382(10):970-971. PMID: 32003551external icon
https://pubmed.ncbi.nlm.nih.gov/32003551/

Asymptomatic Viral Load

  • Zou L, Ruan F, Huang M, et al. SARS-CoV-2 Viral Load in Upper Respiratory Specimens of Infected Patients. The New England journal of medicine. 2020;382(12):1177-1179. PMID: 32074444
https://pubmed.ncbi.nlm.nih.gov/32074444/

Asymptomatic Spread; Cluster Spread

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  • Pan X, Chen D, Xia Y, et al. Asymptomatic cases in a family cluster with SARS-CoV-2 infection. The Lancet Infectious diseases. 2020. PMID: 32087116
https://pubmed.ncbi.nlm.nih.gov/32087116/

Asymptomatic Spread

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  • Bai Y, Yao L, Wei T, et al. Presumed Asymptomatic Carrier Transmission of COVID-19. Jama. 2020. PMID: 32083643
https://pubmed.ncbi.nlm.nih.gov/32083643/

Asymptomatic Spread; Cluster Spread

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  • Kimball A HK, Arons M, et al. Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020. MMWR Morbidity and mortality weekly report. 2020; ePub: 27 March 2020. PMID: 32240128
https://pubmed.ncbi.nlm.nih.gov/32240128/

Asymptomatic Spread; Cluster Spread

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  • Wei WE LZ, Chiew CJ, Yong SE, Toh MP, Lee VJ. Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020. MMWR Morbidity and Mortality Weekly Report. 2020;ePub: 1 April 2020. PMID: 32271722
https://pubmed.ncbi.nlm.nih.gov/32271722/

Asymptomatic Spread; Cluster Spread

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  • Li R, Pei S, Chen B, et al. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science (New York, NY). 2020. PMID: 32179701
https://pubmed.ncbi.nlm.nih.gov/32179701/

Asymptomatic Spread; Cluster Spread

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  • Furukawa NW, Brooks JT, Sobel J. Evidence Supporting Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 While Presymptomatic or Asymptomatic [published online ahead of print, 2020 May 4]. Emerg Infect Dis. 2020;26(7):10.3201/eid2607.201595. Link
https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article

Asymptomatic Spread; Cluster Spread

  • Oran DP, Topol Prevalence of Asymptomatic SARS-CoV-2 Infection: A Narrative Review [published online ahead of print, 2020 Jun 3]. Ann Intern Med. 2020;M20-3012. PMID: 32491919
https://pubmed.ncbi.nlm.nih.gov/32491919/

Surgical Mask Efficacy: "These findings suggest that surgical face masks could reduce the transmission of human coronavirus and influenza infections if worn by infected individuals capable of transmitting the infection"

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  • National Academies of Sciences, Engineering, and Medicine. 2020. Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020). Washington, DC: The National Academies Press. https://doi.org/10.17226/25769
https://www.nap.edu/catalog/25769/rapid-expert-consultation-on-the-possibility-of-bioaerosol-spread-of-sars-cov-2-for-the-covid-19-pandemic-april-1-2020


  • Schwartz KL, Murti M, Finkelstein M, et al. Lack of COVID-19 transmission on an international flight. CMAJ. 2020;192(15):E410. PMID: 32392504
https://pubmed.ncbi.nlm.nih.gov/32392504/

Droplets created from normal speech


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  • Anfinrud P, Stadnytskyi V, Bax CE, Bax A. Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering. N Engl J Med. 2020 Apr 15. doi:10.1056/NEJMc2007800. PMID: 32294341
https://pubmed.ncbi.nlm.nih.gov/32294341/

Laboratory Validated Efficacy of Homemade Face Coverings to Reduce Droplet Transmission: "Overall, our study suggests that cloth face coverings, especially with multiple layers, may help reduce droplet transmission of respiratory infections."

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  • Davies A, Thompson KA, Giri K, Kafatos G, Walker J, Bennett ATesting the efficacy of homemade masks: would they protect in an influenza pandemic? Disaster Med Public Health Prep. 2013;7(4):413-8. PMID: 24229526
https://pubmed.ncbi.nlm.nih.gov/24229526/

Efficacy of homemade cloth face masks regarding aerosol viral particles



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  • Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, Guha S. Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano. 2020 Apr 24. PMID: 32329337
https://pubmed.ncbi.nlm.nih.gov/32329337/

Experiments with mask materials


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  • Ma QX, Shan H, Zhang HL, Li GM, Yang RM, Chen JM. Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2. J Med Virol. 2020. PMID: 32232986
https://pubmed.ncbi.nlm.nih.gov/32232986/

Reducing Viral Shedding via Surgical Face Masks



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  • Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al.Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med. 2020. PMID: 32371934
https://pubmed.ncbi.nlm.nih.gov/32371934/

Reducing Viral Shed of Influenza is Equal Between Surgical and N95 Face Masks

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  • Johnson DF, Druce JD, Birch C, Grayson ML. A quantitative assessment of the efficacy of surgical and N95 masks to filter influenza virus in patients with acute influenza infection. Clin Infect Dis. 2009 Jul 15;49(2):275-7. PMID: 19522650
https://pubmed.ncbi.nlm.nih.gov/19522650/

Reducing Viral Shedding via Surgical Face Masks: "Conclusions: The arrestance of airborne vegetative cells and endospores by surgical masks worn by simulated contagious patients supports surgical mask use as one of the recommended cough etiquette interventions to limit the transmission of airborne infectious agents."

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  • Green CF, Davidson CS, Panlilio AL, et al. Effectiveness of selected surgical masks in arresting vegetative cells and endospores when worn by simulated contagious patients. Infect Control Hosp Epidemiol. 2012;33(5):487‐494. PMID: 22476275external icon
https://pubmed.ncbi.nlm.nih.gov/22476275/

Here is a video that demonstrates how airlflow and fluid dynamics are affected by simple cloth face coverings. 
  

More articles:

https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818

https://www.cmaj.ca/content/192/15/E410

https://www.researchgate.net/publication/342198360_Association_of_country-wide_coronavirus_mortality_with_demographics_testing_lockdowns_and_public_wearing_of_masks_Update_June_15_2020

https://www.nature.com/articles/s41591-020-0843-2#Sec3

https://www.nejm.org/doi/full/10.1056/NEJMc2007800

https://www.washingtonpost.com/business/2020/06/17/masks-salons-missouri/

https://www.medrxiv.org/content/10.1101/2020.04.17.20069567v2.full.pdf

https://news.wisc.edu/coughing-visualization-illustrates-the-benefits-of-wearing-a-good-mask/

https://podcasts.google.com/?feed=aHR0cHM6Ly9mZWVkcy5ucHIub3JnLzUxMDM1MS9wb2RjYXN0LnhtbA&ep=14&episode=ZTNkYmFkNTAtNjhkMi00NmMyLWI0NzMtYjdhNjJiMDE5OTFm

OSHA has put out a statement clarifying the difference between personal protective equipment and cloth face coverings for the use of reducing the spread of coated 19 in communities.

https://www.osha.gov/SLTC/covid-19/covid-19-faq.html

"Cloth face coverings:

May be commercially produced or improvised (i.e., homemade) garments, scarves, bandanas, or items made from t-shirts or other fabrics.
Are worn in public over the nose and mouth to contain the wearer's potentially infectious respiratory droplets produced when an infected person coughs, sneezes, or talks and to limit the spread of SARS-CoV-2, the virus that causes Coronavirus Disease 2019 (COVID-19), to others.
Are not considered personal protective equipment (PPE).
Will not protect the wearer against airborne transmissible infectious agents due to loose fit and lack of seal or inadequate filtration.
Are not appropriate substitutes for PPE such as respirators (e.g., N95 respirators) or medical face masks (e.g., surgical masks) in workplaces where respirators or face masks are recommended or required to protect the wearer.
May be used by almost any worker, although those who have trouble breathing or are otherwise unable to put on or remove a mask without assistance should not wear one.
May be disposable or reusable after proper washing."

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