After weeks of advising most Americans there was no need to wear protective face masks, federal officials on Friday reversed their previous guidance, urging everyone to wear “non-medical cloth” face coverings outside their homes to curb the spread of the coronavirus.
But President Trump appeared to quickly undercut the recommendations of the US Centers for Disease Control and Prevention.
“This is voluntary,” Trump told reporters at the White House, after announcing the recommendation. “I don’t think I’m going to be doing it.”
Before Friday, the CDC had advised that only those who are sick — or caring for someone who is — wear a face mask.
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"Face masks may be in short supply and they should be saved for caregivers,” the CDC website stated.
In late February, the US surgeon general was more blunt. “STOP BUYING MASKS!” the surgeon general, Jerome M. Adams, wrote on Twitter. "They are NOT effective in preventing general public from catching #Coronavirus, but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk!
That advice changed this week when the CDC, in a draft document first reported by STAT, recommended that Americans start wearing homemade face masks, reserving medical-grade masks for health care workers.
The coverings would mainly serve to protect the wearers from spreading the coronavirus, especially if they lack symptoms and don’t know they have the disease. The CDC is now suggesting people wear them in public, when they go shopping, visit pharmacies, or may be in close proximity with others.
The policy shift was welcome, if late, many specialists say.
“The debate is over; we should be wearing face masks,” said Joseph Allen, an assistant professor of exposure assessment science at the Harvard T. H. Chan School of Public Health. “We should be taking a precautionary principle, and we didn’t start early enough.”
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Allen cited four reasons everyone should be wearing protective face coverings — even simple masks composed of cotton T-shirts — in public.
— Masks worn by the infected could act as a physical barrier to prevent dangerous droplets from being transmitted to others or falling on surfaces.
— Homemade face coverings could substantially reduce the chance of a healthy person inhaling the virus from someone who is infected, he said.
— They serve as a physical reminder that people shouldn’t touch their eyes, nose, or mouth.
— They also serve a social cue, reminding everyone that we’re living through a dangerous pandemic and that we should be keeping our distance from each other.
The CDC’s reversal comes after cities and states were moving ahead on their own. On Wednesday, the mayor of Los Angeles urged residents to wear masks in public, and on Friday, New York’s mayor did as well.
Federal officials had advised against face masks largely out of concern that people would buy up gear essential for health care workers, some of which has been in low supply; false assurance that they would be fully protected and wouldn’t also engage in social distancing; and concerns that people could infect themselves by constantly touching their faces to adjust the masks.
But Allen and others cited recent studies that suggest the potential benefits far outweigh the risks.
Edward Nardell, a professor at Harvard Medical School who studies infectious diseases, was on a commission of the National Academy of Medicine that recently submitted a report to the White House, advising the president to urge all Americans to wear face coverings.
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“At this point, there’s no good reason not to wear them,” said Nardell, who’s among the thousands of Americans now recovering from COVID-19. “Even though homemade masks don’t guarantee protection from infection, they probably provide some protection by reducing the velocity of the air we’re sucking in.”
In a press briefing on Thursday, Trump said, “If people wanted to wear them, they can.”
He added: “If people wanted to use scarves, which they have, many people have them, they can. In many cases the scarf is better. It’s thicker.”
Allen said scarves, which are often porous, don’t offer as much protection as a simple cotton shirt or other cloth.
In an interview on FOX News on Friday, Dr. Anthony Fauci of Trump’s coronavirus task force said new findings that the virus could be spread as an aerosol while people are speaking led him to believe that Americans should be wearing face coverings in public.
"The better part of valor, when you’re out and you can’t maintain that 6-foot distance, is to wear some type of facial covering,” he said.
In urging city residents to wear cloth face coverings, New York City Mayor Bill de Blasio suggested they get creative. “It can be as homemade as you want,” he said in an interview on MSNBC on Friday, adding that only health care workers should be collecting medical-grade masks.
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But some specialists said government officials should go a step further and mandate the use of masks in public places, as is the case in some Asian countries that have been more successful at containing the spread of the disease.
Jeremy Howard, a research scientist at the University of San Francisco who specializes in medical data analytics, said there’s now overwhelming evidence from Asia that the spread of the virus declines when a majority of the population wears masks.
“Suggesting people not wear masks is like suggesting people shouldn’t have worn condoms at the height of the HIV crisis,” he said. “It’s basically encouraging people to engage in harmful behavior.”
A few weeks ago, David Hamer, an infectious disease specialist at Boston Medical Center, wasn’t recommending that non-infected people wear masks. He has since changed his views.
“We know more now,” he said.
He also suggested that public officials start wearing masks at press conferences or when they’re interacting with the public, to set the right example.
“We have to start changing the culture on this,” he said.
David Abel can be reached at david.abel@globe.com. Follow him on Twitter @davabel.