East Bay Getting to Zero

Universal face coverings are a key part of a safer reopening!

All of us wearing face coverings and maintaining at least 6 feet of distance whenever outside our homes or personal vehicles is necessary for a safer reopening. 

COVID-19 cases increased in May in the East Bay, and we all must help protect each other to contain the spread. Other counties in California have loosened their restrictions at a faster pace than the Bay Area because they are less densely populated and have lower burdens of disease. Alameda County now has the highest case count in the Bay Area, and we can’t let this number grow too fast.    

Face coverings are one of the lowest-cost and most effective ways to prevent the spread of COVID-19. If we all wear face coverings in combination with physical distancing, hand hygiene, testing and contact tracing, we can more safely ease restrictions and return to work and school.

My face covering protects you, and your face covering protects me. Face coverings are best at preventing respiratory droplets coming out of the wearer’s nose and mouth from reaching other people. Homemade coverings provide some protection for the wearer too, though not as much as medical-grade surgical masks or N95 masks, which should be reserved for medical settings.

Recommended materials for face coverings:

  • Covering your nose and mouth with any breathable fabric reduces transmission of respiratory droplets compared to no covering.
  • Most double-layer cotton and similar fabrics block more than 90% of droplets from being emitted.
  • Even a single-layer of t-shirt fabric can block more than 70% of droplets.
  • If using cotton or cotton-blend fabric, quilting-weight or heavy-weight fabrics block better than thinner fabrics.
  • If you use a bandana, the fabric is usually quite thin, so we recommend using at least a double layer with a filter layer in between (see filter recommendations below).
  • Non-woven polypropylene from matte reusable grocery bags can also be used, particularly as an outer layer with repellent properties.
  • Filters: Non-woven polypropylene can also be used as a reusable/washable filter. Other single-use filter materials that are commonly used are disposable coffee filters and paper towels. Be careful using vacuum bag material and avoid any containing fiberglass, which is dangerous when inhaled.

Instructions to make your own face coverings and masks:

Wearing and washing face coverings:

  • The better the covering fits around the nose, chin and cheeks without gaps, the better it blocks.
  • Sterilize or wash reusable coverings before first use. To sterilize, boil in water for 10 minutes.
  • To wash reusable coverings, use the hottest water and drier setting that is safe for the material. Coverings can also be washed in hot water and dried in bright sunlight for disinfection.
  • Wash or sanitize your hands before and after you put the covering on.
  • Take face coverings off using the ear loops or straps and avoid touching the outside surface before you put it in the wash.
  • Use once before washing or discarding: Wash reusable face coverings or discard disposable ones after one trip out in the community.

Why should we all wear face coverings?

  1. Anyone could have and transmit COVID-19, including many people without symptoms. In US screening studies, up to 88% of people with COVID-19 didn’t have symptoms.   
  1. Respiratory droplets carrying the COVID-19 virus can travel more than 6 feet (up to 26 feet with a sneeze!), and we don’t always maintain 6 or more feet of distance. 
  1. Face coverings, including homemade ones, are effective in blocking droplets from being emitted, such as from talking, singing, sneezing and coughing. This is called “source control.”
    • Most double-layer cotton and similar fabrics block more than 90% of droplets from being emitted. Even a single-layer of t-shirt fabric can block more than 70% of droplets. Non-woven polypropylene from matte reusable grocery bags can also be used, particularly as an outer layer with repellent properties. The better the covering fits around the nose, chin and cheeks, the better it blocks.
    • Math models suggest that if most of us wear masks that are at least 60% effective, we will reduce the transmission rate (Ro) from about 2.4 to below 1.0. This means each infected person would infect fewer than one other person, and the disease will eventually die out.
    • Cloth face coverings should be cleaned after each use (especially in crowded areas) by washing with detergent in hot water and drying in a hot dryer or in direct sunlight. Clean or sanitize hands before and after handling face coverings.


Do we have to wear face coverings if we intend to stay or work 6 feet apart?

  • Yes, we need to wear face coverings in combination with at least 6 feet of distance. Neither of these interventions alone is perfect, so we need to use them in combination.

Do we have to wear face coverings when working or exercising outdoors?

  • Yes, when outdoors we need to wear face coverings and maintain distance. While air circulation is better outdoors, and we may not intend to get close or talk with others, be prepared when it happens by wearing a face covering.

Can we wear our face mask or covering below or nose or mouth, especially in between contacts?

  • Face coverings need to cover your nose and chin. The masks or coverings should fit well over the bridge of your nose, around the side of your cheeks, and below your chin. Respiratory droplets are exhaled and inhaled through both the nose and mouth. You may expose yourself to inhaling droplets that have gotten on the outside of your covering this way. 

Please reserve medical masks (surgical/loop masks and N95 masks) for people who really need them, such as those who are sick and health care workers.

Wearing face coverings whenever we leave our homes is a good habit we will need for the next two years.


Asymptomatic COVID-19 in up to 88% of people with SARS-CoV-2

Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill. 2020;25(10):2000180. doi:10.2807/1560-7917.ES.2020.25.10.2000180

Baggett TP, Keyes H, Sporn N, Gaeta JM. Prevalence of SARS-CoV-2 Infection in Residents of a Large Homeless Shelter in Boston [published online ahead of print, 2020 Apr 27]. JAMA. 2020;e206887. doi:10.1001/jama.2020.6887

Sutton D, Fuchs K, D’Alton M, Goffman D. Universal Screening for SARS-CoV-2 in Women Admitted for Delivery [published online ahead of print, 2020 Apr 13]. N Engl J Med. 2020;NEJMc2009316. doi:10.1056/NEJMc2009316

He, X., Lau, E.H.Y., Wu, P. et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med 26, 672–675 (2020). https://doi.org/10.1038/s41591-020-0869-5

COVID-19 respiratory droplet transmission

Bourouiba L. Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19. JAMA. 2020;323(18):1837–1838. doi:10.1001/jama.2020.4756

Hamburger M Jr, Robertson OH. Expulsion of group A hemolytic streptococci in droplets and droplet nuclei by sneezing, coughing and talking. Am J Med. 1948;4(5):690‐701. doi:10.1016/s0002-9343(48)90392-1

Read R. A choir decided to go ahead with rehearsal. Now dozens of members have COVID-19 and two are dead. Los Angeles Times2020;29th March 2020. Accessed 27th April 2020 at https://www.latimes.com/world-nation/story/2020-03-29/coronavirus-choir-outbreak

Video of respiratory droplets traveling from a sneeze: https://jamanetwork.com/journals/jama/fullarticle/2763852

Face coverings are effective against COVID-19 transmission

Gandhi M, Havlir D. The Time for Universal Masking of the Public for Coronavirus Disease 2019 Is Now. Open Forum Infect Dis. 2020;7(4):ofaa131. Published 2020 Apr 15. doi:10.1093/ofid/ofaa131

Howard, J.; Huang, A.; Li, Z.; Tufekci, Z.; Zdimal, V.; van der Westhuizen, H.; von Delft, A.; Price, A.; Fridman, L.; Tang, L.; Tang, V.; Watson, G.L.; Bax, C.E.; Shaikh, R.; Questier, F.; Hernandez, D.; Chu, L.F.; Ramirez, C.M.; Rimoin, A.W. Face Masks Against COVID-19: An Evidence Review. Preprints 2020, 2020040203 (doi: 10.20944/preprints202004.0203.v2).

Davies A, Thompson K-A, Giri K, et al. Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Disaster medicine and public health preparedness2013;7(4):413-18.

Rengasamy S, Eimer B, Shaffer RE. 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 2010;54(7):789-98.

van der Sande M, Teunis P, Sabel R. Professional and home-made face masks reduce exposure to respiratory infections among the general population. PLoS One 2008;3(7)

Dato VM, Hostler D, Hahn ME. Simple Respiratory Mask: Simple Respiratory Mask. Emerging Infectious Diseases 2006;12(6):1033.

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 26, 676–680 (2020). https://doi.org/10.1038/s41591-020-0843-2