Football coaches do it. The elected presidents do it. Even academically savvy senators do. As coronavirus cases continue to rise around the world, some of the country’s most famous people have begun doubling down on masks – a move that researchers say is increasingly being backed by data.

Double masking is not necessary for everyone. But for people with thin or thin face coverings, “When you combine layers, you get pretty high levels of efficiency” by preventing viruses from leaking out of the airways and into the airways, said Linsey Marr, virus transmission expert at Virginia Tech and author of a recent commentary describes the science behind mask wearing.

Of course there is a compromise: at some point we run the risk of making it too difficult to breathe, she said. But there is plenty of room to breathe before mask wearing approaches this extreme.

A year after the Covid-19 pandemic, the world looks very different. More than 90 million confirmed coronavirus infections have been documented worldwide, leaving millions dead and countless others with lingering symptoms in ongoing economic hardship and closed schools and businesses. New variants of the virus have emerged that bring about genetic changes that appear to improve their ability to spread from person to person.

And while several vaccines have now cleared regulatory hurdles, injections adoption has been stuttering and slow – and there’s still no definitive evidence that gunshots will have a significant impact on how quickly and by whom the virus spreads.

Through all of these changes, researchers have kept the line with masks. “Americans don’t have to wear masks forever,” said Dr. Monica Gandhi, an infectious disease doctor at the University of California at San Francisco and author of the new comment. But for now they have to stay and offer protection to both those wearing the mask and the people around them.

The case for masking spans several areas of science, including epidemiology and physics. A host of observational studies have shown that the widespread use of masks can curb infection and death on an impressive scale, in settings as small as hair salons and at the country level. A study that tracked government policies that make face coverings mandatory in public found that known Covid cases with mask-wearing rules increased and decreased almost in lockstep. Another who followed coronavirus infections among health care workers in Boston saw a drastic decrease in the number of positive test results after masks became a universal part of the workforce. A study in Beijing found that face masks were 79 percent effective at blocking transmission from infected people to their close contacts.

Recent work by researchers like Dr. Marr now lay down the basis of these links on a microscopic scale. The science, she said, is pretty intuitive: respiratory viruses like the coronavirus, which move between people in spit and spray marks, need clear piping to get into the airways, which are overcrowded with the types of cells that the viruses infect. Masks that cover the nose and mouth prevent this invasion.

It’s not about making a mask airtight, said Dr. Marr. Instead, the fibers that make up masks create a random obstacle course that air – and any contagious cargo – must navigate.

“The air must follow this tortuous path,” said Dr. Marr. “The great things it bears will not be able to follow these turns.”

Experiments testing the ability of masks to block incoming and outgoing spray showed that even relatively simple materials, such as fabric covers and surgical masks, can be at least 50 percent effective in either direction.

Several studies have reinforced the notion that masks seem to protect people around the mask wearer better than mask wearers themselves. “That’s because you stop it at the source,” said Dr. Marr. Based on the latest research, the Centers for Disease Control and Prevention has found that there are great benefits for those who wear masks too.

The best masks remain N95, which are designed with ultra-high filtration efficiency. However, they are still in short supply for health workers who need them to safely treat patients.

Layering two less specialized masks can provide comparable protection. Dr. Marr recommended wearing face masks over surgical masks, which are typically made from more filter-friendly materials but fit more loosely. An alternative is to wear a cloth mask with a pocket that can be filled with filter material, as is the case with vacuum bags.

However, wearing more than two masks or applying masks that can already filter very well quickly leads to falling yields and makes normal breathing considerably more difficult.

Other improvements can improve the fit of a mask, e.g. B. Ties that secure the fabric at the back of the head instead of relying on ear loops to allow masks to hang and gape. Nose bridges, which can help the top of a mask fit tighter, also provide a protection boost.

Achieving great fit and filtration “is really easy,” said Dr. Gandhi. “It doesn’t have to contain anything special.”

No mask is perfect, and wearing a mask does not prevent other public health measures such as physical distancing and good hygiene. “We have to be honest that the best answer is one that requires multiple interventions,” said Jennifer Nuzzo, a public health expert at Johns Hopkins University.

Wearing masks is uncommon in some parts of the country, partly due to the politicization of the practice. However, experts found that the model behavior of heads of state and government could help turn the tide. In December, President-elect Joseph R. Biden Jr. pleaded with Americans to wear masks during his first 100 days in office and said he would make it compulsory in federal buildings as well as on planes, trains, and buses crossing state lines .

A comprehensive review of the evidence for masking published this month in PNAS magazine concluded that masks are a key tool in reducing community transmission and are “most effective at reducing the spread of the virus with high compliance.”

Some of the messages may also require more empathy, open communication, and voice recognition that “people don’t wear masks,” said Dr. Nuzzo. Without more patience and compassion, simply doubling the limits to “fix” poor compliance will backfire: “No policy will work if no one adheres to it.”

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