Wearing two masks at once can offer more protection against potential coronavirus transmission and exposure than donning a single mask, the US Centers for Disease Control and Prevention (CDC) has advised.
In a report published this week, CDC researchers said exposure to potentially infectious aerosols decreased by about 95 percent when a cloth mask was worn over a medical procedure mask, a practice also known as double-masking.
To provide the same protection, a mask can also be worn by knotting the ear loops of a medical procedure mask and then tucking in and flattening any extra material close to the face.
The key, the report found, is to ensure the masks fit tightly.
“Medical procedure masks are intended to provide source control (eg, maintain the sterility of a surgical field) and to block splashes,” it said.
“The extent to which they reduce exhalation and inhalation of particles in the aerosol size range varies substantially, in part because air can leak around their edges, especially through the side gaps.”
As new, more virulent strains of COVID-19 have emerged in countries around the world, many public figures have been seen wearing two face masks instead of one, including US President Joe Biden.
The country’s top infectious disease expert, Dr Anthony Fauci, has called it “common sense” to wear two masks. “This is a physical covering to prevent droplets and virus to get in,” Fauci told NBC’s Today show.
“If you have a physical covering with one layer, if you put another layer on it, it just makes common sense that it likely would be more effective and that’s why you see people either double masking or doing a version of an N95 [mask].”
Layers of filtration
The CDC’s report is in line with earlier research by two US-based experts who, in a December article published in the scientific journal, Med, recommended wearing a “a cloth mask tightly on top of a surgical mask”.
“If your simple cloth mask filters out 50 percent of particles, then layering two of them on top of each other will increase the efficiency to about 75 percent,” said Linsey Marr, professor of civil and environmental engineering at Virginia Tech who studies viruses in the air, and co-author of the report.
“The surgical-type mask is a good filter but may not fit very well, and the cloth mask adds another layer of filtration and, more importantly, improves the fit by reducing gaps and leaks especially around the cheeks and nose,” Marr told Al Jazeera.
Marr said masks will block the new strains with the same efficiency as they did with previous variants.
The key point is that people infected with new variants release more virus particles into the air than individuals infected with previous strains, and it takes fewer virus particles from the new variants to cause infections, Marr said.
No official recommendation
The World Health Organization (WHO) has not yet officially recommended double-masking, however.
In its latest interim guidance published in December, the WHO said the general public should wear a non-medical mask where physical distancing of at least one metre cannot be maintained in areas suspected of community transmission.
At an online briefing last week, WHO infectious disease physician Joshua Barocas said there is “ample evidence” that masks help reduce transmission of the coronavirus.
“At this point, we’ve got studies from aeroplanes, hospitals and other congregate settings that provide ample evidence on the importance of masks,” Barocas said.
“These are places where transmission is potentially highest, but we know that when mask mandates and broad mask-wearing have been implemented, it has decreased transmission, and this is likely even more important with emerging variants.”
Controversy over mask orders
Health experts say masks help reduce potential coronavirus transmission, but orders mandating their use have been controversial in the US and other countries.
The imposition of rules enforcing mask-wearing over the past year have sparked a backlash, with some perceiving the orders as an affront to personal liberties. Others have railed against people who refuse to wear face coverings, accusing them of endangering public health.
Throughout the pandemic, guidelines around mask-wearing have shifted as public health experts’ understanding of the virus evolved.
In the early weeks of the outbreak in the US, officials including the country’s surgeon general urged the public not to buy masks, saying they did not need them or would not know how to wear them – and thus would gain a false sense of security.
Then, in April, the CDC recommended Americans wear “cloth face coverings fashioned from household items or made at home from common materials … as an additional, voluntary public health measure”.
Former President Donald Trump was not seen wearing a mask until July, and during the presidential election campaign, he mocked Biden for wearing one.
Meanwhile, health misinformation has flourished on social media since the beginning of the pandemic and some conspiracy theorists have falsely claimed the changing mask directives prove the pandemic is a hoax.
Marr listed several reasons as to why the US guidelines have evolved over the past year.
Initially, there was a shortage of respirators and masks for healthcare workers, so there was a reluctance to recommend them for the public, she said. Additionally, Trump regularly disputed the importance of masks and their efficacy, contradicting health officials.
Public health agencies were also slow to acknowledge the virus could spread through the air.
“There was a lack of understanding, outside the small community of aerosol scientists, about the ability of masks to work in both directions and to work for the size of respiratory aerosols that are most concerning,” Marr said.
Biden’s mask mandate
Now, with the US still reporting the most coronavirus-related deaths and cases in the world by a wide margin, Biden has made mask-wearing a central pillar of his strategy to get the pandemic under control.
The country has recorded more than 27.2 million infections and more than 470,000 deaths to date. Last month, it hit a new record for daily infections, recording 290,000 new cases in just 24 hours, according to a tally by John Hopkins University. But in recent weeks, the numbers of daily cases and hospitalisations have steadily declined.
Biden unveiled a “wartime strategy” to confront the health crisis at the start of his term.
Amid a flurry of executive actions, he ordered a mask mandate on federal property for federal employees, and also ordered government agencies to “immediately take action” to require masks to be worn in airports and on public transportation.
The CDC subsequently issued new rules ordering masks on nearly all forms of public transport.
Mask-wearing outside the home recently reached an all-time high in the US at 80 percent, according to a survey conducted by experts at Harvard, Northwestern, Northeastern and Rutgers universities in December and January.
The researchers surveyed 25,640 people across all 50 US States, as well as Washington, DC, between December 16 and January 11.
But David Lazer, a professor at Northeastern University and one of the survey authors, told NPR last month that more needs to be done to reduce the spread of the virus.
“The good news is we’ve improved a lot in terms of mask-wearing and social distancing. The bad news is, to bend the curve they really need to be much better,” Lazer said.
Wendy Parmet, Professor of Law and faculty director of the Center for Health Policy and Law at Northeastern University in Boston told Al Jazeera that mask wearing has become highly politicised and polarising.
A significant group of the population views the lack of mask wearing as a political statement or a sign of their political identity.
Parmet said it’s now critical for the Biden administration to ramp up the messaging and get the word out on the importance of mask wearing in multiple forums and to issue public service announcements. “No single stroke of the pen” is going to get the public to accept mask wearing.
“We need to depoliticise in some sense the pandemic and stop viewing relatively easy public health measures as hot-button political issues,” Parmet said.
“The irony for mask-wearing is that for people who want to keep businesses open and the economy moving despite the pandemic, mask wearing is the easy win, it’s the easy step and much less draconian than other restrictions.
“It should have been the non-partisan, we-can-all-agree-upon step, but unfortunately it wasn’t viewed that way [during the Trump administration] and it’s hard to put the toothpaste back into the tube.”