Federal health officials asked Americans on Wednesday to keep their masks on and take steps to make them more fit – or even a layer of cloth covering a surgical mask – saying new research has shown that masks greatly reduce spread of the coronavirus.
Recent laboratory experiments found that viral transmission could be reduced by 96.5% if Americans wore tight surgical masks or a combination of cloth and surgical mask. In announcing the findings, Dr. Rochelle P. Walensky, director of the Centers for Disease Control and Prevention, implored Americans to wear a “tight-fitting mask”.
“With cases, hospitalizations and deaths still very high, now is not the time to reverse mask requirements,” she said. “The main point is this: the masks work, and they work when they have a good fit and are used correctly.”
Masking is now mandatory on federal properties and on domestic and international transportation. Studies conducted in residences in Beijing, hair salons in Missouri and on board an aircraft carrier in Guam have proved that “any mask is better than none,” said Dr. John T. Brooks, medical director of response at Covid in CDC and lead author of the agency’s new research on masking.
“The use of a mask reduces the spread and, in communities that adopt the use of a mask, new infections decrease,” said Brooks.
But while masks reduce respiratory droplets and aerosols exhaled by infected users and protect uninfected ones, leaking air around the edges of a mask can reduce its effectiveness. The agency’s new laboratory experiments showed how to solve the problem.
One option is to wear a cloth mask over a surgical mask, the agency said. The alternative is to adjust the surgical mask more firmly on the face by “knotting and folding” – that is, tying the two strands of the ear loops where they attach to the edge of the mask and then folding and flattening the extra tissue in the edge of the mask and folding it for a firmer seal.
The agency’s experiments were based on surgical masks and three-layer tissue, and only one type of each mask was tested. Other combinations – such as folding into cloth masks or wearing two surgical masks, or overlaying a surgical mask over a cloth mask – have not been tested.
The advice comes even when states began to suspend measures to delay transmission of the virus. About three dozen states have masking requirements, but on Monday, Iowa ended its term, joining Mississippi and North Dakota, which it did months ago.
States are rushing to restart business and reopen schools. Governor Andrew Cuomo of New York, for example, announced on Wednesday that fans will be able to return to stadiums and arenas for sporting events and shows, with limited capacity, with mandatory testing and seating. New York City will allow indoor meals to resume on Friday, at 25% capacity.
Virus-related deaths, which resurfaced sharply in the United States in November and remain high, appear to be steadily declining. New cases and hospitalizations also started to drop last month.
But the CDC warned that, even with the decline in cases, the new variants could increase infections if Americans let their guard down. The cases of a more contagious virus variant found for the first time in Britain are doubling approximately every 10 days in the United States. The CDC warned last month that it could become the dominant variant in the country in March.
Until the vast majority of adults are vaccinated, “we want to suppress this,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University. Masks are an easy and effective way to do this, avoiding another catastrophic “roller coaster,” he added.
“The fewer opportunities we give this virus to multiply, the less likely it is that mutations will occur and the less likely we will have new variants,” said Dr. Schaffner.
Dr. Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, co-authored an article on how to make masks more effective that inspired the CDC to conduct the new research.
“We want to do our best to contain the transmission using all the elements: masking, distance, hand hygiene, ventilation,” she said. “If we reduce transmission and vaccinate en masse at the same time, the virus will not have an opportunity to escape the vaccine.”
The CDC described some additional options for improving the effectiveness of the masks, including the use of a mask adjuster – a frame with the outline of the face – over a mask. Recent studies have found that adapters can increase protection against aerosols containing viruses by 90% or more.
Surprisingly, perhaps, the agency also suggested that people consider wearing a transparent nylon mesh sleeve around the neck and pulled over a cloth or surgical mask.
The CDC’s recommendations were based in part on ideas articulated by Dr. Gandhi and Linsey Marr, an aerosol transmission specialist at Virginia Tech. The two recommended a surgical mask covered by a tight-fitting fabric mask or a three-layer fabric mask consisting of two outer layers of tightly woven fabric that hug the face and an intermediate layer of filter material, such as a vacuum bag.
Both tight fit and filtration are important, Marr said. Even with a N95 breathing mask, the type used by healthcare professionals, a good fit is essential.
Although a growing number of Americans say they support the use of masks, resistance continues in some circles and regions. Dr. Marr said she hoped the new CDC council would be ridiculed.
“I’m sure the resistance will say, ‘What’s next? Three masks? Four masks? ‘”Said Marr. “But there is a lot of interest from people who want to know how good their masks are and how they can make them better. People want the best possible protection. “
The CDC experiments simulated the production of aerosols from a cough and estimated their absorption. While a knotless surgical mask blocked 42 percent of the particles and a cloth mask blocked 44.3 percent, the combination of a cloth mask over a surgical mask blocked 92.5 percent of the coughed particles, Dr. Brooks and his colleagues colleagues found out.
When the aerosol source and the exposed form were equipped with a combination of masks or with a folded surgical mask and knots, exposure to the receiver was reduced by 96.4% and 95.9%.
Neither method was perfect: knotting and folding makes the mask’s surface smaller and may be more appropriate for people with smaller faces, Dr. Brooks noted.
Likewise, the combination of cloth and surgical mask works well, but makes the mask thicker and can make it difficult for some people to breathe. Additional layers can also obstruct peripheral vision, increasing the risk of tripping or falling.
Breathability is also important, said Dr. Marr. “If you put too many layers on top of each other that make it difficult to breathe, it is counterproductive: the air is more likely to find cracks to enter,” she said.
Dr. Brooks emphasized that masking, as Americans currently practice it, is not “insufficient”. But the new council offers “an opportunity to move to the next level”.
“We are now concerned with the forms of the virus that can be transmitted more efficiently or impair the usefulness of existing diagnostics, therapies and vaccines,” he added. “We need to improve our game to slow the spread of the virus and its evolution.”
Sheryl Gay Stolberg contributed reporting from Washington.