Thread by @DocJeffD

With more dangerous CoV-19 variants, we must improve CoV-19 prevention in all aspects of our lives, incl. mask quality & fit, limiting time w/others, avoiding crowded indoor spaces, increasing distance from others, & getting vaccinated when it’s your turn. On masks: 1/

Cloth masks are recommended by CDC for use by the public. Cloth face masks were initially recommended to prevent someone w/CoV-19 from spreading the virus to others. This is especially important because people can spread the infection to others before they appear or feel ill. 2/

Recent studies suggest cloth face masks can also provide protection to the wearer. How well it protects depends on how well it's made & fits (e.g. the type & # layers of fabric). At this time, CDC only recommends N95 masks & surgical masks for health care workers (HCW) 3/

Studies show that multiple layers of cloth w/higher thread counts (tighter weave) have demonstrated superior performance compared to single layers of cloth with lower thread counts. Some other materials, such as polypropylene and silk, also can enhance the quality of a mask. 4/

Most important considerations when selecting a cloth mask include:
•2-3 fabric layers
•Made of tightly woven fabrics such as cotton/cotton blends
•Breathable
•Snug fit without gaps
•Comfortable to wear the consistently whenever around others outside the home. 5/

Cloth masks should have 2 or more layers. Some masks have an option for a paper filter inside which adds a 2nd or 3rd layer. Wearing 2 masks (double masking), with a tighter-fighting mask on top, is another way to add layers to improve filtration and help create a snug fit. 6/

This can include at least 2 layers of face-covering material with a good cloth mask or (non-medical grade) surgical-type mask on the bottom & a tightly-woven material that conforms to the face on top. Great reference: cell.com/med/pdf/S2666-… 7/

Mask layers should allow the breath should go through the mask & not around the sides or out the top. If your glasses fog or breath goes around the sides, the fit should be better. See the CDC’s scientific brief on cloth masks: cdc.gov/coronavirus/20… 8/

At this time, CDC only recommends N95 masks & surgical masks for HCW & not the public. N95 masks are very effective in healthcare settings when fit-tested to ensure no air leaks & worn properly but are expensive & remain in short supply. 9/

If sufficient/affordable supplies were available, N95 or similar masks might be an option for use by the public, particularly in high-risk settings, although it's not clear what level of protection is needed in most settings or how well N95 work without fit testing. 10/

Medical-grade surgical masks (aka procedure masks) may provide protection superior or comparable to good quality multi-layered cloth masks. Surgical masks are recommended by CDC for HCW & not for the public. Non-medical grade masks are sold widely (? quality). 11/

There are lots of masks available that are sold as "surgical masks," & it can be difficult to determine the quality of these masks. The quality of protection that a surgical mask provides highly depends on the manufacturer and fit. 12/

Surgical-type masks do not always fit snugly & can be used with another tighter mask on top or a device like Fix the Mask (fixthemask.com) to improve the fit against the face and prevent air leaking out the sides.
Again, cell.com/med/pdf/S2666-… 13/

KN95 are Chinese-made masks w/effectiveness theoretically similar to N95 although there are reports of poor quality control/performance & counterfeit KN95 being sold on the internet. We don't have enough evidence to make a recommendation for use of KN95 or similar masks. 14/

Cloth & surgical-type masks available to the public aren't always medical grade/quality. HCP have access to medical-grade masks & can work w/their healthcare system, employee health, &/or infection prevention specialists to find the best mask & fit for their work environment. 15/

Would love to see updated CDC guidance regarding strategies to improve the quality/fit/effectiveness of cloth masks & whether surgical masks/KN95/non-medical N95s masks should be considered for the public and if so, how to evaluate them for quality. 16/16

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