CDC Recommends Masks to Limit Community Spread of COVID-19
Asymptomatic transmission causes CDC to change guidance on mask use.
Several scientific studies that track the spread of COVID-19 through groups of people show that spread by people with few or no symptoms is happening. This means that everyone needs to act as though they have the virus and can spread it to someone else. You can’t be sure just from a lack of symptoms that you do not have the virus.
In light of these studies, CDC is now recommending homemade face masks for people who are
in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission.
The Surgeon General even shows in a video how to make a homemade face mask or “cloth face covering” as CDC calls it. What is lacking is information about how to ensure that the mask is used safely.
[Update 15 April 2020: More information about properly wearing and using face masks and homemade face coverings and several options for making face coverings have been added to the CDC site. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html]
Most people will not throw away the cloth mask after wearing it. This means that cloth face masks need to be cleaned after use.
Anyone who chooses to wear a homemade cloth mask should be sure to consider the mask contaminated with the virus after wearing it.
Fortunately, the coronavirus is easy to kill with warm soapy water. After wearing a cloth mask, the mask should be removed carefully, washed with warm soapy water, and the wearer should wash his or her hands thoroughly.
People in an essential business, especially someone who will be in contact with many members of the community, like cashiers or workers in grocery stores and pharmacies, may need to wear a mask day after day. They should have several. That way, when one mask is being washed or is drying, a clean one is available.
The CDC video shows how to make a cloth mask using a piece of cloth and 2 rubber bands. The video below shows how to make masks using T-shirts. Additionally, it describes how to use a paper towel as an additional layer of barrier that can be disposed after use. The video also explains removing the mask and washing the mask after use and washing up after wearing. The video goes through some of the scientific data supporting mask use and materials for effective masks. If you want to fast-forward to the DIY mask instructions, go to 6:45 in the video.
As the scientist, Jeremy Howard, in this video explains: Your mask saves me and my mask saves you.
Wearing a clean mask can help reduce community spread of an upper respiratory contagious disease. But wearing a mask does not mean you could not spread the virus or get the virus. It reduces the risk. The key to breaking the transmission chain is social distancing and isolation to prevent contact between uninfected and infected people.
Research Supporting Mask Use
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A. Davies, K. Thompson, K. Giri, G. Kafatos, J. Walker, A. Bennett. Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic? Disaster Medicine and Public Health Preparedness 7, 413–418 (2013). DOI: 10.1017/dmp.2013.43
E. Einav, ‘Stealth Transmission’ of COVID-19 Demands Widespread Mask Usage. Medscape (29 March 2020). https://www.medscape.com/viewarticle/927723
R. Li, S. Pei, B. Chen, Y. Song, T. Zhang, W. Yang, J. Shaman, Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2) [published 2020 March 16]. Science eabb3221 (2020). DOI:10.1126/science.abb3221
C. Rothe, M. Schunk, P. Sothmann, G. Bretzel, G. Froeschl, C. Wallrauch, T. Zimmer, V. Thiel, C. Janke, W. Guggemos, M. Seilmaier, C. Drosten, P. Vollmar, K. Zwirglmaier, S. Zange, R. Wölfel, M. Hoelscher, Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany. New England Journal of Medicine. 382, 970–971 (2020). DOI: 10.1056/NEJMc2001468
A. Kimball, K. M. Hatfield, M. Arons, A. James, J. Taylor, K. Spicer, A. C. Bardossy, L. P. Oakley, S. Tanwar, Z. Chisty, J. M. Bell, M. Methner, J. Harney, K. R. Jacobs, C. M. Carlson, H. P. McLaughlin, N. Stone, S. Clark, C. Brostrom-Smith, L. C. Page, M. Kay, J. Lewis, D. Russell, B. Hiatt, J. Gant, J. S. Cuchin, T. A. Clark, M. A. Honein, S. C. Reddy, J. A. Jernigan, Public Health — Seattle & King County; CDC COVID-19 Investigation Team, Asymptomatic and Presymptomatic SARS-CoV-2 Infections in Residents of a Long-Term Care Skilled Nursing Facility — King County, Washington, March 2020. MMWR Morbibity and Mortality Weekly Report 69, 377–381 (2020). DOI: 10.15585/mmwr.mm6913e1
Z.-D. Tong, A. Tang, K.-F. Li, P. Li, H.-L. Wang, J.-P. Yi, Y.-L. Zang, J.-Bo Yan, Potential Presymptomatic Transmission of SARS-CoV-2, Zhejiang Province, China, 2020. Emerging Infectious Diseases 26, 10.3201/eid2605.200198 (2020). DOI: 10.3201/eid2605.200198