Engineering:Cloth face mask

From HandWiki
Short description: Mask made of common textiles worn over the mouth and nose
Cloth face mask
Clothfacemask101.jpeg
A cloth face mask made out of 2-ply construction with layers of 85% polyester and 15% cotton fabric
Other namesFabric mask

A cloth face mask is a mask made of common textiles, usually cotton, worn over the mouth and nose. When more effective masks are not available, and when physical distancing is impossible, cloth face masks are recommended by public health agencies for disease "source control" in epidemic situations to protect others from virus laden droplets in infected mask wearers' breath, coughs, and sneezes. Because they are less effective than N95 masks, surgical masks, or physical distancing in protecting the wearer against viruses, they are not considered to be personal protective equipment by public health agencies. They are used by the general public in household and community settings as protection against both infectious diseases and particulate air pollution.

Cloth face masks were routinely used by healthcare workers starting from the late 19th century until the mid 20th century. In the 1960s they fell out of use in the developed world in favor of disposable surgical masks with an electret (electrically charged) filter material, but cloth masks persisted in developing countries. During the COVID-19 pandemic, their use in developed countries was revived due to shortages, as well as for environmental concerns and practicality. Launderable cloth electret filters were also being developed.[1]

Usage

Guidance from the U.S. Centers for Disease Control and Prevention on using and making cloth masks during the COVID-19 pandemic[2]

Prior to the COVID-19 pandemic, reusable cloth face masks were predominantly used by healthcare workers in developing countries and were especially prominent in Asia. Cloth face masks contrast with surgical masks and respirators such as N95 masks, which are made of nonwoven fabric formed through a melt blowing process, and are regulated for their effectiveness based upon efficiency of minimum particle size filtered and/or maximum penetrating particle (MPP) size, along with other criteria such as outer splash/spray protection, inner splash/spray absorption, contaminant accumulation and shedding, air flow, and inflammability.[3] Like surgical masks, and unlike respirators, cloth face masks do not provide a seal around the face, and prior to the 2019 COVID-19 outbreak were generally not authorized by institutions for protection from sub-HEPA particle size (less than 0.3 um) Influenza Like Illness (ILI).[4]

In healthcare settings, they are used on sick patients as source control to reduce disease transmission through respiratory droplets, and by healthcare workers when surgical masks and respirators are unavailable. Cloth face masks are only recommended for use by healthcare workers as a last resort if supplies of surgical masks and respirators are exhausted.[4] They are also used by the general public in household and community settings as perceived protection against both infectious diseases and particulate air pollution and to contain the wearer's exhaled virus laden droplets.[4][5]

Several types of cloth face masks are available commercially, especially in Asia.[5] Homemade masks can also be improvised using bandanas,[2] T-shirts,[2][3] handkerchiefs,[3] scarves,[3] or towels.[6] But depending on the situation, reusable cloth masks with incorporated filters can block particles nearly as well as medical-grade masks can, as long as they fit securely.[7]

Recommendations

Infographic from the World Health Organization showing the do's and don'ts of wearing a fabric mask to prevent the spread of COVID-19
Two French cloth masks certified by AFNOR. The white mask is made of polypropylene and the black one is made of cotton.

The World Health Organization (WHO) recommends that cloth face masks should be worn in public where social distancing is not possible to help stop the spread of coronavirus. It notes that wearing a cloth face mask is just one of a range of tools that can be used to reduce the risk of transmission.[8] The US Center for Disease Control, along with Johns Hopkins University School of Medicine, The Mayo Clinic, and Cleveland Clinic all concur with this recommendation.[9][10][11][12] The World Health Organization also recommended that those aged over 60 years old or with underlying health risks require more protection and should wear medical masks in areas where there is community transmission.[8]

The World Health Organization recommends using masks with at least three layers of different materials. Two spunbond polypropylene layers are also believed to offer adequate filtration and breathability.[13] When producing cloth face masks, two parameters should be considered: filtration efficiency of the material and breathability. The filter quality factor known as "Q" is commonly used as an integrated filter quality indicator. It is a function of filtration efficiency and breathability, with higher values indicating better performance. Experts recommend Q-factor of three or higher.[13]

A peer-reviewed summary[14] of the filtration properties of cloth and cloth masks concluded that, pending further research, evidence is strongest for 2 to 4 layers of plain weave cotton or flannel, at least 100 thread count. A plain-language summary of this review is available.

Comparison of materials for fabric masks[13]
Material (source) Structure Initial
Filtration
Efficiency (%) 		Initial
Pressure
drop (Pa) 		Filter
quality
factor, Q
(kPa−1)
Polypropylene (interfacing material) spunbond 6 1.6 16.9
Cotton (sweater) knit 26 17 7.6
Cotton (T-shirt) knit 21 14.5 7.4
Polyester (toddler wrap) knit 17 12.3 6.8
Cotton (T-shirt) woven 5 4.5 5.4
Cellulose (tissue paper) bonded 20 19 5.1
Cellulose (paper towel) bonded 10 11 4.3
Silk (napkin) woven 4 7.3 2.8
Cotton (handkerchief) woven 1.1 9.8 0.48
Cotton, gauze woven 0.7 6.5 0.47
Nylon (exercise pants) woven 23 244 0.4

Effectiveness

Cloth face masks can be used for source control to reduce disease transmission arising from the wearer's respiratory droplets, but are not considered personal protective equipment for the wearer[15][16][17] as they typically have very low filter efficiency.[18][19] There are no standards or regulation for self-made cloth face masks.[19]

As of 2015, there had been no randomized clinical trials or guidance on the use of reusable cloth face masks.[4][6] Most research had been performed in the early 20th century, before disposable surgical masks became prevalent. One 2010 study found that 40–90% of particles in the 20–1000 nm range penetrated a cloth mask and other fabric materials.[18] The performance of cloth face masks varies greatly with the shape, fit, and type of fabric,[5] as well as the fabric fineness and number of layers.[6] As of 2006, no cloth face masks had been cleared by the U.S. Food and Drug Administration for use as surgical masks.[3] A Vietnamese study of healthcare workers compared influenza-like illness outcome among those wearing cloth masks versus medical masks.[20] They concluded that cloth masks were ineffective at preventing transmission in high-risk clinical settings. Although discouraged in clinical settings, cloth masks may still serve a useful role in reducing disease transmission in public settings according to a systematic review.[21]

The primary role of masks worn by the general public is to "stop those who are already infected broadcasting the virus into the air around them."[22] This is of particular importance with the COVID-19 pandemic, as silent transmission seems to be a key feature of its rapid spread. For example, of the people on board the Diamond Princess cruise ship, 634 people were found to be infected—52% had no symptoms at the time of testing, including 18% who never developed symptoms.[23] It is important to note that mask wearers are more likely to engage in other hygiene measures such as hand washing and social distancing. Best practice is to implement multiple prevention techniques to reduce risk, as characterized by the Swiss cheese model.[24]

Compared with bacteria recovery from unmasked volunteers, a mask made of muslin and flannel reduced bacteria recovered on agar sedimentation plates by 99%, total airborne microorganisms by 99%, and bacteria recovered from aerosols (<4 µm) by 88% to 99%.[25] In 1975, 4 medical masks and 1 commercially produced reusable mask made of 4 layers of cotton muslin were compared. Filtration efficiency, assessed by bacterial counts, was 96% to 99% for the medical masks and 99% for the cloth mask; for aerosols (<3.3 µm), it was 72% to 89% and 89%, respectively.[26]

An experiment carried out in 2013 by Public Health England, that country's health-protection agency, found that a commercially made surgical mask filtered 90% of virus particles from the air coughed out by participants, a vacuum cleaner bag filtered out 86%, a tea towel blocked 72% and a cotton t-shirt 51%—though fitting any DIY mask properly and ensuring a good seal around the mouth and nose is crucial.[27][22] The use of common fabrics in making face masks has been tested.[28][29][30][31] Filter efficiency can be improved with multiple layers, high weave density, and a mix of different types of fabrics. Cotton is the most commonly used material, and filter efficiencies can reach >80% for particles <300 nm with fabric combinations such as cotton-silk, cotton-chiffon, or cotton-flannel.[31] The most protective cloth masks need at least three layers with a hydrophilic inner layer (e.g. cotton) to absorb moisture from the wearer's breathing and hydrophobic outer layers (e.g. polyester).[13] Masks should be cleaned after each use. They can either be laundered or hand-washed in soapy hot water and dried with high heat.[32]

History

In 1918, the Red Cross recommended two-layer gauze masks.[33]
During the 1918 flu pandemic, a streetcar conductor in Seattle refuses a person who attempts to board without wearing a mask.

In Roman times, Pliny the Elder recommended that miners use animal bladders to protect against inhaling lead oxides. Some followers of Jainism, which originated in India around 500 B.C.E, wear cloth masks to avoid accidentally inhaling insects as part of practicing ahimsa.[34][35][36] In the 16th century, Leonardo da Vinci advised the use of a wet woven cloth to protect against toxic agents[which?] of chemical warfare.[37] In the early modern period, the plague-doctor costume included a beaked face-mask worn to protect the wearer from infectious "miasma".

Conventional cowboy attire in the American West often included a bandanna, which could protect the face from blown dust and also potentially doubled as a means of obscuring identity.[38]

In 1890 William Stewart Halsted pioneered the use of rubber gloves and surgical face masks, although some European surgeons such as Paul Berger and Jan Mikulicz-Radecki had worn cotton gloves and masks earlier. These masks became commonplace after World War I and the Spanish flu epidemic of 1918.[39][40] Cloth face masks were promoted by Wu Lien-teh in the 1910–11 Manchurian pneumonic plague outbreak, although Western medics doubted their efficacy in preventing the spread of disease.[41]

Cloth masks were largely supplanted by modern surgical masks made of nonwoven fabric in the 1960s,[3][6] although their use continued in developing countries.[4] They were used in Asia during the 2002–2004 SARS outbreak, and in West Africa during the 2013–2016 Ebola epidemic.[4] Compared with bacteria recovery from unmasked volunteers, a mask made of muslin and flannel reduced bacteria recovered on agar sedimentation plates by 99%, total airborne microorganisms by 99%, and bacteria recovered from aerosols (<4 µm) by 88% to 99%.[25] In 1975, 4 medical masks and 1 commercially produced reusable mask made of 4 layers of cotton muslin were compared. Filtration efficiency, assessed by bacterial counts, was 96% to 99% for the medical masks and 99% for the cloth mask; for aerosols (<3.3 µm), it was 72% to 89% and 89%, respectively.[26]

COVID-19 pandemic

Rhode Island National Guardsmen sew face masks during the COVID-19 pandemic, April 6, 2020.

During the COVID-19 pandemic, most countries recommended the use of cloth masks to reduce the spread of the virus.[42]

On June 5, 2020, WHO changed its advice on face masks, recommending that the general public should wear fabric masks where widespread COVID-19 transmission exists and physical distancing is not possible (for example, "on public transport, in shops or in other confined or crowded environments").[43][44]

See also

References

  1. ↑ Godoy, Laura R. Garcia; Jones, Amy E.; Anderson, Taylor N.; Fisher, Cameron L.; Seeley, Kylie M. L.; Beeson, Erynn A.; Zane, Hannah K.; Peterson, Jaime W. et al. (1 May 2020). "Facial protection for healthcare workers during pandemics: a scoping review" (in en). BMJ Global Health 5 (5): e002553. doi:10.1136/bmjgh-2020-002553. ISSN 2059-7908. PMID 32371574. 
  2. ↑ 2.0 2.1 2.2 "Use of Cloth Face Coverings to Help Slow the Spread of COVID-19" (in en-us). April 4, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html.  Template:PD-inline
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Reusability of Facemasks During an Influenza Pandemic: Facing the Flu. Washington, D.C.: National Academies Press. July 24, 2006. pp. 6, 36–38. doi:10.17226/11637. ISBN 978-0-309-10182-0. http://www.nap.edu/catalog/11637. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 MacIntyre, C. R.; Chughtai, A. A. (April 9, 2015). "Facemasks for the prevention of infection in healthcare and community settings" (in en). BMJ 350 (apr09 1): h694. doi:10.1136/bmj.h694. ISSN 1756-1833. PMID 25858901. http://akkie.mods.jp/2019-nCoV/images/c/c0/%E3%82%B5%E3%83%BC%E3%82%B8%E3%82%AB%E3%83%AB%E3%83%9E%E3%82%B9%E3%82%AF%E5%8C%BB%E7%99%82vs%E5%B8%82%E4%B8%AD%E6%84%9F%E6%9F%93%E4%BA%88%E9%98%B2%EF%BC%9A%E7%B7%8F%E8%AA%AC_%282015%2C_MacIntyre%29.pdf. 
  5. ↑ 5.0 5.1 5.2 Shakya, Kabindra M.; Noyes, Alyssa; Kallin, Randa; Peltier, Richard E. (May 1, 2017). "Evaluating the efficacy of cloth facemasks in reducing particulate matter exposure" (in en). Journal of Exposure Science & Environmental Epidemiology 27 (3): 352–357. doi:10.1038/jes.2016.42. ISSN 1559-064X. PMID 27531371. https://www.ceh.org.in/wp-content/uploads/2017/08/1-Shakaya-Face-Masks-JESEE-2016.pdf. 
  6. ↑ 6.0 6.1 6.2 6.3 Chughtai, Abrar Ahmad; Seale, Holly; MacIntyre, Chandini Raina (June 19, 2013). "Use of cloth masks in the practice of infection control – evidence and policy gaps". International Journal of Infection Control 9 (3). doi:10.3396/IJIC.v9i3.020.13. ISSN 1996-9783. http://www.ijic.info/article/view/11366. 
  7. ↑ "The Best Reusable Face Masks" (in en-US). The New York Times. 2022-01-06. ISSN 0362-4331. https://www.nytimes.com/wirecutter/reviews/best-cloth-face-masks/. 
  8. ↑ 8.0 8.1 "Coronavirus: WHO advises to wear masks in public areas". BBC. 6 June 2020. https://www.bbc.com/news/health-52945210. 
  9. ↑ "Recommendation Regarding the Use of Cloth Face Coverings, Especially in Areas of Significant Community-Based Transmission". CDC. 3 April 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html. 
  10. ↑ "5 Myths About Coronavirus and Face Masks, Debunked. Are you wearing yours the right way?". Cleveland Clinic. 4 June 2020. https://health.clevelandclinic.org/5-myths-about-coronavirus-and-face-masks-debunked/. 
  11. ↑ "COVID-19: How much protection do face masks offer?". Mayo Clinic. 28 May 2020. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-mask/art-20485449. 
  12. ↑ "Coronavirus Face Masks & Protection FAQs". Johns Hopkins School of Medicine. 25 June 2020. https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-face-masks-what-you-need-to-know. 
  13. ↑ 13.0 13.1 13.2 13.3 "Advice on the use of masks in the context of COVID-19". WHO. 5 June 2020. https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak. 
  14. ↑ Clase, C.M., Fu, E.L.F., Ashur, A., Beale, R.C.L., Clase, I.A., Dolovich, M.B., Jardine, M.J., Joseph, M., Kansiime, G., Mann, J.F.E., Pecoirs-Filho, R., Winkelmayer, W. C. and Carrero, J. J. Forgotten technology in the COVID-19 pandemic. Filtration properties of cloth and cloth masks: a narrative review. Mayo Clinic Proceedings 2020; https://www.mayoclinicproceedings.org/article/S0025-6196(20)30826-0/fulltext
  15. ↑ Matuschek, Christiane; Moll, Friedrich; Fangerau, Heiner; Fischer, Johannes C.; Zänker, Kurt; van Griensven, Martijn; Schneider, Marion; Kindgen-Milles, Detlef et al. (12 August 2020). "Face masks: benefits and risks during the COVID-19 crisis". European Journal of Medical Research 25 (1): 32. doi:10.1186/s40001-020-00430-5. PMID 32787926. 
  16. ↑ "FAQs on the Emergency Use Authorization for Face Masks (Non-Surgical)" (in en). 2020-04-26. https://www.fda.gov/medical-devices/emergency-situations-medical-devices/faqs-emergency-use-authorization-face-masks-non-surgical. 
  17. ↑ "Meat and Poultry Processing Workers and Employers" (in en-us). 2020-04-26. https://www.cdc.gov/coronavirus/2019-ncov/community/organizations/meat-poultry-processing-workers-employers.html. 
  18. ↑ 18.0 18.1 "Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles". Annals of Occupational Hygiene (Oxford University Press) 54 (7): 789–798. 2010. doi:10.1093/annhyg/meq044. ISSN 0003-4878. PMID 20584862. 
  19. ↑ 19.0 19.1 "Using face masks in the community - Reducing COVID-19 transmission from potentially asymptomatic or pre-symptomatic people through the use of face masks" (in en). 2020-04-08. https://www.ecdc.europa.eu/en/publications-data/using-face-masks-community-reducing-covid-19-transmission. 
  20. ↑ MacIntyre, C. R.; Seale, H.; Dung, T. C.; Hien, N. T.; Nga, P. T.; Chughtai, A. A.; Rahman, B.; Dwyer, D. E. et al. (2015-04-22). "A cluster randomised trial of cloth masks compared with medical masks in healthcare workers". BMJ Open 5 (4): e006577. doi:10.1136/bmjopen-2014-006577. ISSN 2044-6055. PMID 25903751. 
  21. ↑ Template:Cite medRxiv
  22. ↑ 22.0 22.1 "Should the public wear masks to slow the spread of SARS-CoV-2?". The Economist. ISSN 0013-0613. https://www.economist.com/science-and-technology/2020/04/11/should-the-public-wear-masks-to-slow-the-spread-of-sars-cov-2. 
  23. ↑ "How important is "silent spreading" in the covid-19 epidemic?". The Economist. ISSN 0013-0613. https://www.economist.com/science-and-technology/2020/04/11/how-important-is-silent-spreading-in-the-covid-19-epidemic. 
  24. ↑ https://my.clevelandclinic.org/-/scassets/files/org/employer-solutions/covid-19-workplace-safety-faqs.ashx [bare URL PDF]
  25. ↑ 25.0 25.1 Greene VW, Vesley D. Method for evaluating effectiveness of surgical masks. J Bacteriol. 1962;83:663-7. [PMID 13901536]
  26. ↑ 26.0 26.1 Quesnel LB. The efficiency of surgical masks of varying design and composition. Br J Surg. 1975;62:936-40. [PMID 1203649]
  27. ↑ Davies, Anna; Thompson, Katy-Anne; Giri, Karthika; Kafatos, George; Walker, Jimmy; Bennett, Allan (2013-05-22). "Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?". Disaster Medicine and Public Health Preparedness 7 (4): 413–418. doi:10.1017/dmp.2013.43. ISSN 1935-7893. PMID 24229526. 
  28. ↑ van der Sande, Marianne; Teunis, Peter; Sabel, Rob (2008-07-09). Pai, Madhukar. ed. "Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population". PLOS ONE (Public Library of Science (PLoS)) 3 (7): e2618. doi:10.1371/journal.pone.0002618. ISSN 1932-6203. PMID 18612429. Bibcode: 2008PLoSO...3.2618V. 
  29. ↑ Davies, Anna; Thompson, Katy-Anne; Giri, Karthika; Kafatos, George; Walker, Jimmy; Bennett, Allan (2013-05-22). "Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?". Disaster Medicine and Public Health Preparedness (Cambridge University Press (CUP)) 7 (4): 413–418. doi:10.1017/dmp.2013.43. ISSN 1935-7893. PMID 24229526. 
  30. ↑ Rengasamy, S.; Eimer, B.; Shaffer, R. E. (2010-06-28). "Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles". The Annals of Occupational Hygiene (Oxford University Press (OUP)) 54 (7): 789–98. doi:10.1093/annhyg/meq044. ISSN 1475-3162. PMID 20584862. 
  31. ↑ 31.0 31.1 Konda, Abhiteja; Prakash, Abhinav; Moss, Gregory A.; Schmoldt, Michael; Grant, Gregory D.; Guha, Supratik (2020-04-24). "Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks". ACS Nano (American Chemical Society (ACS)) 14 (5): 6339–6347. doi:10.1021/acsnano.0c03252. ISSN 1936-0851. PMID 32329337. 
  32. ↑ "Coronavirus: How to Care for Your Face Mask" (in en). https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-how-to-care-for-your-face-mask. 
  33. ↑ "Gauze Mask to Halt Spread of Plague". The Washington Times: p. 3. 27 September 1918. https://newspaperarchive.com/washington-times-sep-27-1918-p-3/. 
  34. ↑ George, Nirmala (September 11, 2005). "Jain Ascetics Give It All Up for Their Faith". Los Angeles Times. https://www.latimes.com/archives/la-xpm-2005-sep-11-adfg-nun11-story.html. 
  35. ↑ Briggs, Kenneth A. (August 28, 1975). "A Jainist Monk Brings Ascetic Ways Here". New York Times. https://www.nytimes.com/1975/08/28/archives/a-jainist-monk-brings-ascetic-ways-here.html. 
  36. ↑ "Jainism in India". people.uwec.edu. https://people.uwec.edu/ivogeler/w111/articles/jainism.htm. 
  37. ↑ "The History of Respirator". Cambridge Mask Co. March 28, 2016. https://cambridgemask.com/blog/history-of-respirators/. "The idea of using respirators was pioneered by Pliny the Elder in the first century A.D. when he recommended the use of animal bladder to protect Roman miners from inhaling lead oxide dust. Early inventions did not stop with Pliny as in the 16th century, Leonardo da Vinci, advised the use of a wet woven cloth to protect against toxic agents of chemical warfare." 
  38. ↑ Guttmacher, Peter (1995). Legendary Westerns. MetroBooks. p. 17. ISBN 9781567991727. https://books.google.com/books?id=i_4HAQAAMAAJ. Retrieved 21 August 2020. "Before Sam Peckinpah ever wore a bandana , before Paul Newman and Robert Redford ever got into western gear, these gentlemen train robbers [...]" 
  39. ↑ Fielding H. Garrison (1921). History of Medicine (3rd ed.). Philadelphia W.B. Saunders. p. 761. http://www.archive.org/details/3edintroductiont00garruoft. 
  40. ↑ O'Donnell, V. R.; Chinelatto, L. A.; Rodrigues, C.; Hojaij, F. C. (2020). "A brief history of medical uniforms: from ancient history to the COVID-19 time". Rev Col Bras Cir. 47: e20202597. doi:10.1590/0100-6991e-20202597. PMID 32520135. 
  41. ↑ Lynteris, Christos (18 August 2018). "Plague Masks: The Visual Emergence of Anti-Epidemic Personal Protection Equipment". Medical Anthropology 37 (6): 442–457. doi:10.1080/01459740.2017.1423072. ISSN 0145-9740. PMID 30427733. 
  42. ↑ "Which Countries Are Requiring Face Masks?" (in en). https://www.cfr.org/in-brief/which-countries-are-requiring-face-masks. 
  43. ↑ "Advice on the use of masks in the context of COVID-19: Interim guidance". World health Organization. 5 June 2020. p. 7. https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak. "Table 2: Examples of where the general public should be encouraged to use medical and non-medical masks in areas with known or suspected community transmission" 
  44. ↑ "Coronavirus: WHO advises to wear masks in public areas". BBC News. June 6, 2020. https://www.bbc.com/news/health-52945210. "[...] WHO director-general Dr Tedros Adhanom Ghebreyesus said on Friday that 'in light of evolving evidence, the WHO advises that governments should encourage the general public to wear masks where there is widespread transmission and physical distancing is difficult, such as on public transport, in shops or in other confined or crowded environments'." 

External links



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