The Centers for Disease Control and Prevention (CDC) updated its mask guidance on Wednesday to include data from a recent lab experiment that found placing a cloth mask over a surgical mask, as well as using a properly fitted mask, was effective in stopping coronavirus spread.
The update, which was announced by CDC Director Dr. Rochelle Walensky during a White House coronavirus briefing, comes after a lab experiment using simulated respiratory breaths found that placing a cloth mask over a medical procedure mask or using a medical procedure mask with knotted ear loops and tucked in sides decreased exposure to potentially infectious aerosols by about 95%.
The new guidance advises adhering to two important steps, namely making sure the mask fits snugly against the face, and picking a mask with layers to "keep your respiratory droplets in and others' out." Additionally, the CDC advises using a mask with a nose wire, using a mask fitter or brace to improve fit, and checking to ensure there are no gaps where air may flow.
However, at this time, the agency advises against using two disposable masks, as they are "not designed to fit tightly and wearing more than one will not improve fit." It also does not advise combining a KN95 mask with any other mask.
"The bottom line is this, masks work and they work best when they have a good fit and are worn correctly," Walensky said.
The CDC had announced several weeks ago that it was studying whether using two masks was effective in stopping coronavirus spread after Dr. Anthony Fauci, the nation's leading infectious disease expert, had said doing so "makes common sense."
The agency had been waiting to see "hard data" before making any adjustments, Dr. John Brooks, the CDC's chief medical officer of the COVID-19 response, said during an Infectious Diseases Society of America briefing held late last month.