New study shows effectiveness of different types of masks

visualizing effectiveness of masks
Posted at 7:15 PM, Jun 30, 2020
and last updated 2020-06-30 23:15:05-04

CLEVELAND — A new study published Tuesday highlights the importance of wearing masks in containing COVID-19.

The study, published online for the scientific journal Physics of Fluids, contains images that show a manikin modeling different masks. Researchers used a fog or smoke machine to simulate "respiratory jets" or droplets from coughs and sneezes.

The pictures visualize how far those droplets can travel with a mask or without one, and how much air bleeds or leaks from the sides or top of a mask that doesn't fit properly.

Dr. Mark Cameron, an infectious disease researcher and professor at Case Western Reserve University's School of Medicine, said the study shows that "mask usage was far more effective than no mask at all."

Cameron, who leads the virology group for CWRU's COVID-19 task force, said in general, there are two types of studies that can help researchers determine the effectiveness of masks: correlative (which looks at mask use as a whole within a community or among contacts and correlates it with the number of infections in that community) and lab-controlled (where researchers test the viruses or bacteria on the back of a mask after someone uses them).

Cameron said this new study gives a picture of how effective mask use can be, but it also highlights that masks are not 100% foolproof and that other precautions are still necessary.

"If you have a mask on, it's not a perfect shield," Cameron said. "You still have to keep your distance from people. You still have to avoid large gatherings."

According to the study, droplets from coughing or sneezing with a mask on can travel an average of eight feet, beyond the six-foot distance typically observed in social distancing.

visualizing effectiveness of masks
PHOTO: Respiratory jets with no mask.

"The pictures really tell the story," Cameron said. "Anybody could read the paper and see that, 'OK, here's where the virus could escape our mask. Here's where the distance amongst or between us is really important, even if we are wearing a certain type of mask. And the other measures that we need to take are still just as important as putting that mask on.'"

According to the study's results, a bandana made of T-shirt material cuts that distance to slightly more than 3.5 feet, while a folded handkerchief reduces that to one foot, three inches. A stitched cotton mask: just 2.5 inches, while an over-the-counter commercial cone mask, found at drugstores, can allow droplets to go an average of eight inches.

visualizing effectiveness of masks
PHOTO: A mask made of a folded handkerchief.

"It helps instruct us as scientists and hopefully relay that to the community in terms of mask usage and how a mask has to fit and the potential types of materials that can best protect us," Cameron said.

Cameron said that stay-at-home orders and a return to work for many people have likely contributed to an uptick in Ohio's cases, keeping the state at a plateau rather than coming down the curve.

"What has surprised us as epidemiologists is the length of time that it's taken from reversing the stay-at-home orders and gradually going back to work in some of our daily activities, and the case numbers that are posted accordingly," Cameron said.

He said enough states have shown similar patterns to demonstrate "that the end of stay-at-home orders were really responsible, first and foremost, for the upswing in cases that we're seeing now."

But that's taken longer than epidemiologists imagined.

"It's taken up to a month. For example, some of the new cases we're seeing today in Ohio could still be downstream infections from Memorial Day weekend or have occurred in workplaces that went back to work a few weeks ago," Cameron said. "And now we're starting to see the accumulation of those cases and they're showing up in our daily case count."

While Ohio remains around its plateau, Cameron said he hopes Ohio isn't entering a second wave.

"I hope that it's not just luck alone that is keeping Ohio around its plateau," Cameron said. "But we should also be disappointed. We should be learning more. We should be truly bending our curve and coming down the other side."

To him, that highlights the importance of using a mask in addition to social distancing and avoiding large gatherings.

"Compliance has got to stay up here," Cameron said. "People have to understand that the facial covering is effective to this degree and have to understand on the basis of these studies what some of the gaps in mask usage are."

If the number of cases continues to rise, Cameron said there may be no choice but to pause reopening, "re-shuttering some of the businesses and going back on to stay-at-home orders, which none of us want to do."

He added that people also "have to be cognizant of where we are. So, for example, if we're in a closed environment, in a restaurant, in a booth with other air circulation, and they've seen examples of that, even with mask usage, it's possible that the virus can escape that mask and circulate in the air."

"That, again, gives us some evidence that our outdoor activities, our outdoor seating, restaurants that use tables outside are mostly, are going to be the most effective in containing the virus," Cameron said.

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