The Evidence on Face Masks
Several decades of research informs the current recommendations.
Posted Apr 11, 2020
Since the U.S. Centers for Disease Control recommended that Americans wear face masks when they go out in public, it’s likely that you are noticing a variety of face coverings – bandanas, homemade fabric masks, medical-grade masks and more – when you venture out.
The recommendations came after researchers learned that the coronavirus, which has led to more than 100,000 deaths worldwide, spreads via droplets produced when someone coughs, sneezes or even simply speaks, and that people can spread the virus without having any symptoms.
A systematic review published in 2009 combined the data from 59 studies to assess physical interventions that prevent the spread of respiratory viruses.
The review found that frequent hand washing, disinfecting surfaces, and wearing a mask were among the most effective ways to prevent the spread of respiratory viruses.
A second systematic review was published earlier this year looking at how well masks protect against respiratory viruses. Because this study is newer, it has not yet undergone the peer review process. This review combined the data from 21 studies examining whether the use of masks reduces the risk of contracting a respiratory virus. This review found that the use of masks can reduce the risk of a respiratory infection by up to 80 percent. Masks had a protective effect against the coronavirus and the previous SARS virus that led to a global pandemic in 2003.
The CDC recommends the general public use cloth face coverings made from household items or from common materials found at home and save the medical-grade face masks for health care workers.
They recommend that cloth face coverings fit snugly against the side of the face, be secured with ties or ear loops, include multiple layers of fabric, allow for breathing without restriction and be washable.
The take-home message: Wearing some type of cloth mask over your face when you are out in public can protect you and help reduce the spread of the virus. But the CDC warns that wearing a mask does not replace social distancing, such as avoiding unnecessary outings and staying at least six feet away from people in public places.
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