As states reopen from stay-at-home orders, many, including California, are now requiring people to wear face coverings in most public spaces to reduce the spread of COVID-19. Both the Centers for Disease Control and Prevention (CDC) and the World Health Organization now recommend cloth masks for the general public, but earlier in the pandemic, both organizations recommended just the opposite. These shifting guidelines may have sowed confusion among the public about the utility of masks. But health experts say the evidence is clear that masks can help prevent the spread of COVID-19 and that the more people wearing masks, the better. We talked to UC San Francisco epidemiologist George Rutherford, MD, an infectious disease specialist Peter Chin-Hong, MD, about the CDC’s reversal on mask-wearing, the current science on how face masks work, and what to consider when choosing an N95 face mask, or KN95 face mask, FFP2 face mask or FFP3 mask respirator.
Why did the CDC change its guidance on wearing masks?
The original CDC guidance partly was based on what was thought to be low disease prevalence earlier in the pandemic, said Chin-Hong.
“So, of course, you’re preaching that the juice isn’t worth the squeeze to have the whole population wear masks in the beginning – but that was a reflection of not having enough testing, anyway,” he said. “We were getting a false sense of security.”
Rutherford was blunter. The legitimate concern that the limited supply of surgical masks and N95 mask respirators should be saved for health care workers should not have prevented more nuanced messaging about the benefits of masking. “We should have told people to wear cloth masks right off the bat,” he said.
Another factor “is that culturally, the U.S. wasn’t prepared to wear masks,” unlike some countries in Asia where the practice is more common, said Chin-Hong. Even now, some Americans are choosing to ignore CDC guidance and local mandates on masks, a hesitation that Chin-Hong says is “foolhardy.”
What may have finally convinced the CDC to change its guidance in favor of masks were rising disease prevalence and a clearer understanding that both pre-symptomatic and asymptomatic transmission is possible – even common. Studies have found that viral load peaks in the days before symptoms begin and that speaking is enough to expel virus-carrying droplets.
“I think the biggest thing with COVID now that shapes all of this guidance on masks is that we can’t tell who’s infected,” said Chin-Hong. “You can’t look in a crowd and say, oh, that person should wear masks. There’s a lot of asymptomatic infection, so everybody has to wear a mask.”
The World Health Organization (WHO) on Friday released guidelines on the use of masks as controversy swirls in some countries due to political leaders’ remarks over their use.
WHO releases guidelines on mask use against COVID-19
WHO director-general Tedros Adhanom Ghebreyesus said at a thrice-weekly video press conference that he wanted to talk about who should wear masks, what materials they should be made of, and when they should be worn.
“I wish to be very clear that the guidance we are publishing today is an update of what we have been saying for months: That masks should only ever be used as part of a comprehensive strategy in the fight against COVID-19,” said Tedros.
“In the light of evolving evidence, WHO advises that governments should encourage the general public to wear masks where there are widespread transmission and physical distancing is difficult, such as on public transport, in shops or other confined or crowded environments,” he said.
Based on new academic research, Tedros said the WHO advised people to wear masks consisting of at least three layers of different materials, as outlined in the guidelines, if wearing fabric variants.
He cautioned, however, that “masks on their own will not protect humanity from COVID-19, and the WHO continues to recommend that people who are sick with symptoms of the virus should remain at home and should consult their health care provider.”
The WHO was asked about any guidance for political leaders in the US, where it was noted some key leaders at the White House did have masks on at a press conference Friday.
President Donald Trump has also publicly expressed his distaste for wearing masks in front of journalists.
“This guidance is given as guidance to our member states and it must be interpreted and adapted by national authorities accordingly,” said WHO’s executive director of health emergencies, Dr. Mike Ryan.
“We have no specific advice for any specific grouping at the country level other than certain occupational hazards or other areas like health care, where we believe there’s a significant excess risk and then in that situation, we advise very specifically, the type of mass to be used.”
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