CDC Scientific Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2 (11-10-20)

[TomCADem]

It is unfortunate that folks can't be flexible, particularly on the right in the face of evidence that masks help prevent the spread of COVID-19. Unfortunately, simple prevention has become highly politicized due in large part to Trump actively spreading misinformation on COVID-19.

https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html#:~:text=Background,of%20SARS%2DCoV%2D2.

Background
SARS-CoV-2 infection is transmitted predominately by respiratory droplets generated when people cough, sneeze, sing, talk, or breathe. CDC recommends community use of masks, specifically non-valved multi-layer cloth masks, to prevent transmission of SARS-CoV-2. Masks are primarily intended to reduce the emission of virus-laden droplets (“source control”), which is especially relevant for asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others, and who are estimated to account for more than 50% of transmissions.1,2 Masks also help reduce inhalation of these droplets by the wearer (“filtration for personal protection”). The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects; individual prevention benefit increases with increasing numbers of people using masks consistently and correctly.

Source Control to Block Exhaled Virus
Multi-layer cloth masks block release of exhaled respiratory particles into the environment,3-6 along with the microorganisms these particles carry.7,8 Cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger)9 but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns ;3,5 which increase in number with the volume of speech10-12 and specific types of phonation.13 Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles3,14 and limit the forward spread of those that are not captured.5,6,15,16 Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets,4 with cloth masks in some studies performing on par with surgical masks as barriers for source control.3,9,14

Filtration for Personal Protection
Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns. The relative filtration effectiveness of various masks has varied widely across studies, in large part due to variation in experimental design and particle sizes analyzed. Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles less than 1 micron .14,17-29 Some materials (e.g., polypropylene) may enhance filtering effectiveness by generating triboelectric charge (a form of static electricity) that enhances capture of charged particles18,30 while others (e.g., silk) may help repel moist droplets31 and reduce fabric wetting and thus maintain breathability and comfort.

[ProfessorGAC]

1. K&R

The physical chemistry is irrefutable on this.

[sheshe2]

2. I have been wearing one since March.

It is mandated here. Even if wasn’t I would still wear one.

[TomCADem]

3. I Think Part of the Problem is That Some Masks Suck

I purchased some early on that did not fit well and were not breathable at all. For example, one I bought from Target was so loose that I felt like I was inhaling the mask itself like a gag.

However, after going through a couple, I found some that fit well and are breathable. However, I am sure a lot of folks tried one that did not fit well and just gave up.

[sheshe2]

4. My sister made dozens for family.

She is a retired nurse and designed them after the ones she wore in ICU. They are double layer cotton, trifold to bring it over the chin. I’ll admit they did take some getting used to… However they’re fine now. 😷😷😷

[Midnight Writer]

5. Yes, my sister, too. Masks were hard to get. She made sure her family and friends were "covered".

White cotton, triple layer, with nose pieces (pipe cleaners) and filter pockets.

Not very elegant, but I was sure thankful for her thoughtfulness.

[Hermit-The-Prog]

6. Whatever happened to 3M ramping up production of N95s? Hospitals still short?

Nurses, orderlies, doctors, etc. shouldn't have to be making their own at this point.

[ProfessorGAC]

7. They Did

But, because the maladministration let the inventory collapse, a lot of the product is going to backfill the strategic inventories at the federal & state level.
We can't afford, as a country, to just keep the line filled with no strategic reserves. So, even though they've maxxed out production, it won't be enough day to day until that reserve hits safety minimums.

[Hermit-The-Prog]

8. Thank you!

[Blue_true]

9. Anyone who still claim that mask wearing don't help people either avoid

COVID19, or lessens the severity, is an idiot. The issue that I would like to see addressed in a systematic way is what types of masks (other than the respirator masks) are most effective, design, materials, nose wire versus no nose wire, ect. Such information can be invaluable to consumers, who now have to deal with patchwork and sometimes questionable “evaluations” that often have too much subjectivity involved with them. Also, efforts need to be made to develop safe and effective “athletic” face masks, the ones on the market now saturate when a person sweats and become difficult to keep on (breathing is difficult and the slide around).