Updated at 1:30 p.m. ET
The Centers for Disease Control and Prevention released new research on Wednesday that found wearing a cloth mask over a surgical mask offers more protection against the coronavirus, as does tying knots on the ear loops of surgical masks. Those findings prompted new guidance on how to improve mask fit at a time of concern over fast-spreading variants of the virus.
For optimal protection, the CDC says to make sure the mask fits snugly against your face and to choose a mask with at least two layers.
In laboratory testing, researchers simulated coughs and breathing and tested how well different masks worked to block aerosol particles — comparing no mask, a cloth mask or a surgical mask. They also tested two methods to optimize the fit of cloth and medical masks: wearing a cloth mask over a surgical mask, and tying knots on the ear loops of surgical masks and then tucking in and flattening the extra material against the face.
Both methods produced substantially improved protection against transmission of and exposure to infectious aerosols.