En español | The Centers for Disease Control and Prevention (CDC) has updated its guidance on the use of cloth face masks to prevent the spread of coronavirus, now saying that beyond protecting others the practice can help safeguard the wearer from infection.
Since April, the federal health agency has encouraged all Americans — even people who feel healthy — to wear valveless, multilayered cloth masks when out in public to help slow the spread of SARS-CoV-2, the virus that causes the COVID-19 illness. The masks can limit respiratory droplets released when a person sneezes, coughs, sings, talks or breathes from dispersing into the air, which is the predominant way the virus is spread, according to the CDC.
Face masks also provide “personal protection” to wearers, acting as a filter to reduce respiratory droplets from being inhaled, according to the latest CDC guidance. The federal health agency made the determination based on recent research. It also comes as the U.S. surpassed 10 million confirmed infections, with daily cases on the rise in 49 states — soaring well beyond 120,000 per day.
On Nov. 8, Utah became the 34th state to require people to wear face coverings in public to curb the spread of COVID-19. In general, the state orders require masks in restaurants and stores, on public transit, in taxis and ride-hailing services, and outdoors when it is difficult to maintain 6 feet of distance from others.
The CDC stresses that it is important for people who feel healthy to follow the mask-wearing advice because more than half of transmissions are estimated to occur from individuals with COVID-19 who do not have symptoms, according to the CDC.
Masks save money as well as lives
The American Medical Association (AMA) on Wednesday reasserted its calls for the public to do its part to reduce the spread of the coronavirus.
"We implore everyone to follow these three simple science- and evidence-based steps to help stop the spread of COVID-19: Wash your hands, practice physical distancing and wear a mask,” AMA President Susan R. Bailey, M.D., said in a statement. “Cases are at record highs across the country, and with the holidays quickly approaching, each of us must do everything possible to reduce the spread of COVID-19. Failing to do our part will prolong the suffering and disruption to our lives, and inevitably lead to more deaths of our friends, neighbors and loved ones."
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Beyond saving lives, the CDC guidance suggests mask wearing may also be good for the economy, saying that if mask use is adopted by an additional 15 percent of Americans it could “prevent the need for lockdowns and reduce associated losses of up to $1 trillion, or about 5 percent of gross domestic product."
Mounting evidence of masks’ effectiveness
The CDC's revised guidance suggesting face masks offer protection to the wearer is based on the latest research into how the coronavirus is spread. In particular, it pointed to a study involving more than 1,000 people in Thailand who were interviewed as part of contract tracing investigations. Those who always wore masks were substantially less likely to have been infected than those who never wore masks, the CDC said.
Another investigation showed that a universal mask policy at a hair salon in Springfield, Missouri, protected clients of two stylists who were ill with COVID-19. Over an eight-day period, the stylists interacted with 139 clients an average of 15 minutes each. All of the clients and staff wore masks. Among 67 clients who agreed to an interview and testing, none was infected.
Researchers have also found that multilayered, cotton fabric face masks are effective filters of respiratory droplets.
"Upwards of 80 percent blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control,” the CDC guidance says.
Studies have shown that multiple layers of cotton fabric with higher thread counts (rather than single layers of cloth) filter nearly half of fine particles. Polypropylene can enhance the filtration effect by creating a static electric charge. And silk may help repel moist droplets to reduce fabric wetting and maintain breathability, according to the CDC.