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Not only is the covid-19 vaccine here, but mutant and more transmissible variants of covid-19 are also making their presence known. In the wake of all this, scientists are now urging people to wear a surgical mask along with a cloth mask—in an effort to double the protection.
Scientists have agreed for some time the main way the virus is spread is through the air, rather than surfaces, and there’s growing evidence that small droplets from ordinary breathing and speech that can travel many meters are a common mode of transmission.
Added to this is the greater contagiousness of emerging variants, like B.1.1.7, which takes a smaller viral load to cause symptomatic covid-19 compared to the more common strain.
Back when authorities first recommended people wear face coverings, proper masks were in extremely short supply and the public was encouraged to fashion makeshift solutions out of T-shirts or bandanas. But these are far from ideal.
Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, who studies airborne disease transmission, told AFP, “How well a mask works depends on two things: filtration and fit.”
“Good filtration removes as many particles as possible, and a good fit means that there are no leaks around the sides of your mask, where air— and viruses—can leak through,” she said, adding even a small gap could lead to a 50% reduction in performance.
The best materials for blocking small particles include non-woven polypropylene, which is used to make N95s and many surgical-type masks, and the HEPA filters in planes. Among fabrics, tightly woven cotton works best, she added.
“If you wear a cloth mask, choose one that has multiple layers, ideally one with a pocket that you can slip a good filter material into,” said Marr. “Or you can double mask by wearing a surgical-type mask with a tight-fitting cloth mask over it.”
Surgical masks are made of material that filters things out well, but they tend to be loose, so adding a cloth mask on top holds down the edges and reduces leaks.
Adding an additional layer improves filtration—if one layer traps 50%of all particles, combining two gets to 75%.
But, she added, “We do not recommend wearing more than two masks. Adding more layers proves diminishing returns and can compromise breathability. It must remain easy to breathe through the layers; otherwise, air is more likely to leak in around the sides of the mask.”
Masks that have a metal nose bridge help ensure a snug fit, as do straps that tighten around the head, not just the ears. Braces that improve the fit of surgical masks are now available on the market.
“You should feel the mask sucking inward when you breathe in, and if you hold your hands around the sides of the mask, you should not feel any air leaking out when you breathe out,” said Marr.
Another option is getting hold of N95s, or their international equivalents such as KN95, FFP2 etc.
“They all provide a similar level of filtration, meaning protection of particles going in and out,” Ranu Dhillon, a global health physician at Brigham and Women’s Hospital and Harvard Medical School.
Dhillon, who has been advocating in favour of better masks since last spring, is frustrated by the lack of clear messaging to the public on the value of better masks.
What’s more: “There’s not been a concerted push to really mass produce and mass distribute these higher caliber masks.”
With inputs from AFP