Why Cloth Masks May Increase Your Coronavirus Risk

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Woman wearing a mask
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Wearing a cloth mask can protect you from a coronavirus infection, but only if you properly wash the mask after every use.

Hand-washing a cloth mask can double your risk of being infected with pathogens like the coronavirus, compared to machine-washing it in hot water after each use, according to a study from researchers at the Kirby Institute at UNSW Sydney in Australia.

Every time you don a cloth mask or surgical mask, you should consider it contaminated once you are finished wearing it, says Raina MacIntyre, the professor who conducted the study. She adds:

“Unlike surgical masks, which are disposed of after use, cloth masks are re-used. While it can be tempting to use the same mask for multiple days in a row, or to give it a quick hand-wash or wipe-over, our research suggests that this increases the risk of contamination.”

In reaching that conclusion, MacIntyre and other researchers analyzed previously unpublished data from a randomized controlled trial they published in 2015. That study — based on data on hospital health care workers in Vietnam — remains the only one of its kind to look at how effective cloth masks are in preventing viral infections, according to the Kirby Institute.

While the 2015 study did not test for the new coronavirus, the pathogen that causes the COVID-19 disease, it tested for several other viruses that cause respiratory illnesses. These included other coronaviruses as well as influenza and rhinovirus.

The recently published study found that health care workers who washed masks by hand had double the infection risk of those who had their masked washed in the hospital laundry — that is, in a washing machine with hot water and detergent.

MacIntyre notes that the study results support the World Health Organization’s recommendation to machine-wash cloth masks with detergent and hot water of 60 degrees Celsius — or 140 degrees Fahrenheit. Handwashing is not possible at such temperatures, she adds.

There has been some controversy about whether cloth masks offer as much protection as disposable surgical masks. But MacIntyre and the other Kirby Institute researchers say the evidence shows that properly washed cloth masks offer protection as strong as that of surgical masks.

MacIntyre also urges people to check their washing machine settings before laundering cloth masks. She notes that some washing machines have a default setting of only 40 degrees Celsius, or 104 degrees Fahrenheit.

For more about the best options for face masks, check out “The 3 Most Effective — and 2 Least Helpful — Face Masks.”

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