(WSJ) — Face masks are emerging as one of the most powerful weapons to fight the new coronavirus, with growing evidence that facial coverings help prevent transmission—even if an infected wearer is in close contact with others.
Robert Redfield, director of the Centers for Disease Control and Prevention, said he believes the pandemic could be brought under control over the next four to eight weeks if “we could get everybody to wear a mask right now.” His comments, made in mid-July with the Journal of the American Medical Association, followed an editorial he and others wrote there emphasizing “ample evidence” of asymptomatic spread and highlighting new studies showing how masks help reduce transmission.
The research Dr. Redfield cited included a newly published study suggesting that universal use of surgical masks helped reduce rates of confirmed coronavirus infections among health-care workers at the Mass General Brigham health-care system in Massachusetts.
His comments are the clearest message yet from the CDC, amid fierce debate over facial coverings, fueled initially by shifting messages from federal and global officials about their necessity and then by those espousing individual liberties.
The CDC currently recommends the use of cloth face coverings in public, and several states have made the coverings a requirement for most people in wide-ranging public situations. An analysis published Sunday in the BMJ, a medical journal, found that face coverings are now recommended or mandated in 160 countries to reduce coronavirus transmission.
Stemming the Spread
Researchers simulated droplet dispersal from a heavy cough using different types of common masks.
Researchers found that, of the masks they studied, a stitched, double-layered cotton mask was most effective in preventing droplets from being emitted forward. Most of the escape was from the gap between the nose and mask. Droplets traveled further out of the cone mask and also escaped from the top edge
Researchers from around the world have found wearing even a basic cloth face covering is more effective in reducing the spread of coronavirus than wearing nothing at all. And many are now examining the possibility that masks might offer some personal protection from the virus, despite initial thinking that they mostly protect others.
Experts caution that widespread masking doesn’t eliminate the need to follow other recommendations, like frequent handwashing and social distancing.
In the absence of widespread availability of N95 masks—considered among the most effective but typically reserved for health-care workers—transmission can still be reduced with simple and affordable face coverings, the research shows. A case study by Australian researchers published last week in the journal Thorax found that a three-ply surgical mask made of nonwoven material noticeably reduced droplets dispersed while speaking, coughing, and sneezing. The surgical mask proved more effective than two-layer and one-layer cotton facial coverings, the researchers found, noting that efficacy diminished as masks grew thinner.
The study, which analyzed the droplet spread of a healthy volunteer after capturing it on video, hasn’t yet been peer-reviewed. Researchers concluded from their observations that homemade cloth masks likely need several layers—ideally at least three—to prevent the transmission of the virus.
Their findings largely align with a study published last month in the journal Physics of Fluids by researchers at Florida Atlantic University. They found that, of the readily accessible facial coverings they studied, a well-fitted homemade stitched mask comprising two layers of cotton quilting fabric was most effective for reducing the forward spread of droplets. The research was conducted using a mannequin’s head, an air compressor, and a smoke generator that mechanically simulated a cough. This study didn’t evaluate leakage from surgical masks.
The study found that aerosol-size droplets expelled from the mannequin with the double-layered cotton mask traveled forward about 2.5 inches on average, and that most of the leakage escaped from gaps between the nose and face. Loosely fitting facial coverings, including a folded cotton handkerchief with ear loops, as well as a bandanna were less helpful, the study found. With those masks, droplets traveled on average about 1.25 and 3.5 feet, respectively. In contrast, the study found droplets traveled about 8 inches on average with an off-the-shelf cone-shaped mask.
Meanwhile, droplets from an uncovered cough traveled around 8 feet on average, though the study found that they could travel up to 12 feet—double the currently recommended social-distancing guideline of 6 feet.
“It was surprising in a good way to see that a homemade mask could do so well…that we don’t have to get a very fancy mask,” said Siddhartha Verma, one of the study’s co-authors. “A cotton mask can be washed at home and dried. Reusability is becoming important as we go into this for the long haul.”
Dr. Verma and one of his co-authors, Manhar Dhanak, said they are also in the process of putting a laboratory apparatus together to test how much protection various masks might offer to the person wearing them. They plan to study protection against various-sized droplets and particles, as researchers home in on evidence that in addition to large respiratory droplets coronavirus can also be transmitted through aerosol particles that linger in the air.
Exposure is also a focus of researchers now. The amount of virus exposure might influence degree of sickness, according to a review of viral literature and coronavirus epidemiology by Monica Gandhi, a professor of medicine at the University of California, San Francisco. She and her co-authors posit in the research, expected to be published this month in the Journal of General Internal Medicine, that masks provide an important barrier and could lead to a milder infection or even prevent one altogether. While cloth and surgical masks can widely vary, she believes some masks can likely filter out a majority of large viral droplets.
Amy Price, a senior research scientist at Stanford’s Anesthesia Informatics and Media Lab, maintains, in contrast, that the primary benefit of wearing a mask is to protect others and reduce coronavirus transmission. She believes that, excluding N95 masks, multilayered masks with a slightly waterproof outer layer best minimize spread. For an added benefit, she said rubbing the outer layer of the mask with a latex glove before donning it creates static electricity—which Stanford researchers believe can better prevent virus particles from passing from the mouth to outside of the mask.
Researchers are hopeful that more evidence about the personal protection masks could lead to more use in coming weeks. The CDC said the use of cloth face coverings while in public in the U.S. increased to 76.4% in mid-May, compared with 61.9% in April, according to internet surveys sent to roughly 500 adults each month.
Some Americans who have resisted wearing masks have cited health concerns. However, leading medical groups said in a joint statement Thursday, “Individuals with normal lungs, and even many individuals with underlying chronic lung disease, should be able to wear a non-N95 facial covering without affecting their oxygen or carbon-dioxide levels.” Exemptions should be at the discretion of a physician, the groups said.
Researchers say the benefits of widespread mask use were recently seen in a Missouri hair salon, where two stylists directly served 139 clients in May before testing positive for coronavirus. According to a recent report published by the CDC, both wore either a double-layered cotton or surgical mask, and nearly all clients who were interviewed reported wearing masks the entire time.
After contact tracing and two weeks of follow-up, no Covid-19 symptoms were identified among the 139 clients or their secondary contacts, the report found. Of the 67 who were willing to be tested, all were negative for coronavirus.
According to recent projections from the University of Washington’s Institute for Health Metrics and Evaluation, the Covid-19 death toll in the U.S. would rise to nearly 220,000 by November 1. The number is based on expectations that coronavirus mandates will continue to be eased until rising cases prompt shutdowns again in some places. Nearly 147,000 people have died from Covid-19 in the country so far, according to data compiled by Johns Hopkins University.
Yet if 95% of the U.S. population began wearing masks, the expected death toll would drop by nearly 34,000 cases to about 186,000 people, according to IHME.
Wearing a mask is “one of the most urgent things we can do to get our country under control,” said Melanie Ott, director of the Gladstone Institute of Virology. “We’re all waiting for the vaccine, we’re waiting for therapeutics, and we’re not there.”
“We have masks, we have social distancing, and we have testing,” she continued. “But there’s not much more in the toolbox here.”
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