WHO: Fabric masks need 3 layers to best curb coronavirus spread

Crystal Cox/Business Insider
  • New research found that while many types of masks are effective in reducing coronavirus transmission, bandanas do little and fleece masks may backfire.
  • The research follows World Health Organization guidelines, which specify that homemade fabric masks should have three layers, and should be worn and cleaned properly.
  • The guidelines also recommend healthcare workers in areas of wide transmission wear medical masks in clinical settings, even if they're not working directly with COVID-19 patients.
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Now that we know wearing masks is a critical piece of controlling the coronavirus pandemic, researchers are better understanding which types work best.

An August study out of Duke University testing 14 masks, for instance, found that most are effective in reducing particle transmission, but bandanas do little and fleece masks could make coronavirus spread worse.

The findings follow research-backed guidance the World Health Organization released in June. They say fabric masks, either homemade or store-bought, can help prevent the spread of the novel coronavirus — if they have three layers.
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The layers should include an inner layer that absorbs, a middle layer that acts as a filter, and an outer layer made from a non-absorbent material like polyester.

Those layers in that order can "provide a mechanistic barrier," epidemiologist Maria D. Van Kerkhove, the WHO technical lead on COVID-19, said during a media briefing. The guidance, she emphasized, is based on "new, novel research" commissioned by the WHO.

Fabric masks should also be cleaned and worn correctly, since contaminated hands can infect a person adjusting their mask or frequently taking it on or off, Tedros Adhanom Ghebreyesus, the WHO director-general said.
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Different masks are preferable for different people

Matt Cavanagh, a 37-year-old designer, sits on a sidewalk across from his apartment with his chihuahua to get some sun.Crystal Cox / BI Photo

The WHO guidelines encourage people working in clinical settings in areas with widespread coronavirus transmission to wear medical masks — even if they're not working directly with COVID-19 patients. "That means for example, that when a doctor is doing a walk around on the cardiology or palliative care units, where there are no confirmed COVID-19 patients, they should still wear a medical mask," Tedros said.
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The WHO also recommends that caretakers of COVID-positive people wear a medical mask while in the same room as the infected person, and that healthcare workers wear medical masks and other PPE when working with suspected or confirmed COVID-19 patients.

Healthcare workers should get priority when it comes to N95 masks, the CDC says, though the Duke researchers found that polypropylene masks and surgical masks were similarly effective.

People over 60 and with underlying conditions should wear medical masks in areas with community transmission and in settings where physical distancing is difficult, like on public transportation or in a grocery store, the WHO director-general said.
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Masks alone cannot defeat the virus

The WHO mask-wearing guidelines still advise people who are sick with COVID-19 to remain home, consult with their healthcare provider and seek care if necessary, isolate themselves, and have their contacts quarantined.

"If it's absolutely necessary for a sick person or a contact to leave the house, they should wear a medical mask," Tedros said.

And the organization continues to emphasize that masks alone cannot defeat the coronavirus, and can lead to a false sense of security leading people to slack on other important prevention measures.
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"I cannot say this clearly enough: Masks alone will not protect you from COVID-19. Masks are not a replacement for physical distancing, hand hygiene, and other public health measures," Tedros said.

"Masks are only of benefit as part of a comprehensive approach in the fight against COVID-19," he continued. "The cornerstone of the response in every country must be to find, isolate, test, and care for every case, and to trace and quarantine every contact. That's what we know works."

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