The U.S. Centres for Disease Control and Prevention has released new guidance about the best ways to use masks to help prevent transmission of covid-19. One key recommendation highlights the added benefits of using a more snugly fitting mask or pairing a cloth mask with a surgical mask. Experimental data collected by the agency suggests that either option should greatly reduce the risk of transmission between people.
Rochelle Walensky, the newly appointed CDC director, discussed the new recommendations during a White House coronavirus briefing on Wednesday. Walensky first reiterated the current consensus that properly worn masks can help limit the spread of the coronavirus. Some masks are better at protecting the wearer from infection (N95 and KN95 masks in particular), but they all limit the outward transmission of potentially infectious droplets and aerosols to others. New research from the CDC, however, looked at the relative effectiveness of different methods using cloth and surgical masks and how it could be improved.
In the study, even cloth masks were more effective than no masks at limiting the spread of aerosol and droplet particles the size of those emitted by people with covid-19. But surgical masks that were more snugly fit or that had a cloth mask worn on top of them were the most effective at protecting the user and others. In an experiment that simulated being exposed to an infectious person breathing nearby, having both parties wear better-fitted or double-layered masks reduced the level of exposure by more than 95 per cent, Walensky said, compared to no mask at all.
“I want to be clear that these new scientific data released today do not change the specific recommendations about who should wear a mask or when they should wear one, but they do provide new information on why wearing a well-fitting mask is so important to protect you and others,” she added.
The CDC has now updated its website on improving the effectiveness of masks based on this new data. To make surgical masks better-fitting, for instance, the CDC recommends first knotting the strands of the ear loops and tucking in the outer layer of the mask fabric (there’s a helpful guide and visual provided by the CDC if that description isn’t clear enough). There are also other products, such as mask fitters and braces or masks with nose bridges, that will make a mask tighter. However it’s done, you can tell a mask is snug enough if you can feel warm air come through the front of the mask and the mask moves with every breath you take.
As for double-masking, the CDC recommends either wearing a cloth mask with multiple layers or wearing a cloth mask over a surgical mask. However, it doesn’t recommend wearing two surgical masks at once, or combining an KN95 mask with any other mask (to be fair, these masks are already very good at protection when worn correctly).
In addition to wearing masks in public, people should obviously still practice physical distancing whenever possible, avoid crowded indoor spaces, and wash their hands regularly.