Cloth face masks offer two-way protection, benefitting both the wearer and those around them, according to updated guidance from the Centers for Disease Control and Prevention (CDC).
Previously, the CDC had emphasized the role of cloth face masks in blocking the release of infectious virus particles when the wearer coughs, sneezes or talks, thus protecting others from someone who has COVID-19.
But this week, the agency updated its guidelines to say that cloth masks also provide "filtration for personal protection," meaning the masks can filter out potentially infectious droplets from the air, and thus protect the wearer.
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The CDC notes that the effectiveness of cloth masks at filtering particles has varied widely across studies, but masks with multiple layers of cloth and higher thread counts have shown superior protection compared with those that have a single layer and low thread count. In some cases, cloth face masks have been shown to filter nearly 50% of very small particles (less than 1 micron) from the air, the agency said. (Fine droplets, also known as aerosols, are no bigger than 10 microns and are released when people talk, potentially carrying infectious particles.)
In the new guidance, the CDC cited numerous studies suggesting the two-way benefit of masks. For example, in a study of a COVID-19 outbreak on the USS Theodore Roosevelt aircraft carrier, use of face masks on board was tied with a 70% reduction in infection risk.
In addition, several studies have found that state and local mandates for wearing masks in public are tied with significant reductions in new cases.
The CDC concludes that the overall benefit of masking increases as more people in the community wear masks.
"Adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene and adequate ventilation," the agency said.
Originally published on Live Science.
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