Once Americans return to crowded offices, schools, buses and trains, so too will their sneezes and sniffles.
Having been introduced to the idea of wearing masks to protect themselves and others, some Americans are now considering a behavior scarcely seen in the United States but long a fixture in other cultures: routinely wearing a mask when displaying symptoms of a common cold or the flu, even in a future in which Covid-19 isn’t a primary concern.
“I will still feel a responsibility to protect others from my illness when I have a cold or bronchitis or something along those lines,” said Gwydion Suilebhan, a writer and arts administrator in Washington who said he also plans to continue wearing masks in situations like flying on airplanes. “It’s a responsible part of being a human in a civil society to care for the people around you.”
Such routine use of masks has been common for decades in other countries, primarily in East Asia, as protection against allergies or pollution, or as a common courtesy to protect nearby people.
But until the coronavirus crisis, there had seldom been a cultural push for the practice in the United States and several other Western countries. Though masks proved effective in helping mitigate Covid-19 transmission, they now carry weight as symbols in the red state-blue state culture wars, with segments of the country seeing them as an affront to their freedoms and others considering them a demonstration of caring for others.
Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, reflected this week on the future of mask wearing, four days before the Centers for Disease Control and Prevention advised that fully vaccinated Americans may stop wearing masks in most indoor and outdoor settings. “It is conceivable that as we go on, a year or two or more from now, that during certain seasonal periods when you have respiratory-borne viruses like the flu, people might actually elect to wear masks to diminish the likelihood that you’ll spread these respiratory-borne diseases,” he said Sunday on “Meet the Press.”
Other leading American health officials, however, have not encouraged the behavior. The C.D.C. — which at the beginning of the pandemic advised against wearing masks, and only changed its guidance a couple of months later — does not advise people with flu symptoms to wear masks, and says they “may not effectively limit transmission in the community.”
That’s partly because there’s no tidy scientific consensus on the effect of masks on influenza virus transmission, according to experts who have studied it.
Nancy Leung, an epidemiologist at the University of Hong Kong, said that the science exploring possible links between masking and the emission or transmission of influenza viruses was nuanced — and that the nuances were often lost on the general public.
Dr. Leung said the strongest evidence for a connection came from studies that had demonstrated how surgical masks reduced the amount of influenza virus that an infected person emitted, an effect that epidemiologists call “source control.” These studies showed that masking was particularly effective at stopping emission of influenza droplets, she added.
Measuring the impact of wearing surgical masks on community transmission of influenza has been more complicated, she said.
So far, Dr. Leung said, there has been no clear evidence from randomized controlled trials — the gold standard in scientific research — that masking reduced transmission of influenza viruses in a community.
There was some evidence from observational studies that masks reduced community transmission of influenza viruses, she added, but that research had a caveat: Observational studies cannot isolate masking from other possible factors, such as hand hygiene or social distancing.
“You can’t really decipher whether that observed reduction in transmission is due to face masks alone or not,” Dr. Leung said.
For similar reasons, the fact that the flu all but vanished in the United States during the coronavirus pandemic — and that many Americans anecdotally reported that they caught fewer colds than usual in 2020 — is not evidence alone that masks were responsible.
In East Asia, the historical use of masks is based on more than just medical research, and the steps that led each country to adopt them vary widely.
“The mask-wearing culture in the East is related to collectivism,” said Chen Meei-Shia, a public health professor at National Cheng Kung University in Taiwan. “When people face the pandemic as a group, wearing a mask is a way to reduce the individual impact on others.”
De Kai, a computer science professor at the Hong Kong University of Science and Technology who has studied masking etiquette, said that for people in the Chinese territory and elsewhere in East Asia, not wearing a mask while sick would be roughly equivalent to a person “sneezing all over the subway” without covering his or her nose in an American city.
“Of course, nothing’s black and white,” he added. “Clearly it’s a matter of degree. But there is a matter of difference in the East Asian cultures on this versus the very, very libertarian U.S. culture.”
(A reminder: Please sneeze into your elbow, not your hand.)
Others pointed to institutional differences, including a history of anti-masking laws in the United States that were implemented during periods of social unrest in order to discourage violence.
New York State, for example, passed an anti-masking law in 1845 to prevent tenants from demanding land reform, according to research by Sharrona Pearl, a professor of medical ethics at Drexel University in Philadelphia. And from the 1920s to 1950s, several states passed similar laws in response to violence by the Ku Klux Klan.
Several East Asian scholars said in interviews that the region’s mask-wearing customs varied widely because people in each country had responded over the years to different epidemiological or environmental threats.
Jaehwan Hyun, a professor of history of Pusan National University in South Korea, said that ignoring the nuances could be dangerous.
“It enforces the idea of an Asian as a single race maintaining a single mask-wearing culture,” Mr. Hyun said. “I think that’s an easy way to develop discriminatory or racist arguments against Asians.”
In 19th-century Japan, some people wore British-made respirators to guard against colds, coughs and respiratory diseases, said Tomohisa Sumida, a visiting researcher at Keio University. Mask wearing became common after the 1918 influenza pandemic, he added, and again when many people there began to suffer from hay fever allergies in the 1980s.
When South Korea was a Japanese colony in the early 20th century, it inherited some mask-wearing habits from Japan, Mr. Hyun said. Masking was also common in the South Korean capital, Seoul, at points during the 1980s because of factory-related air pollution and the tear gas that accompanied protests against authoritarian rule.
Still, Mr. Hyun said, masking on a regular basis was not common in the country until the mid-2000s, when the government advised the use of an N95-like mask to protect against the seasonal dust storms that sweep into the country from Mongolia and northern China.
“Generally speaking, Koreans until recently believed that mask wearing was a sort of ‘Japanese practice,’ not ours,” he said.
In Hong Kong, where 299 people died during the SARS epidemic of 2002-3, the experience of universal masking against that coronavirus helped create a “cultural familiarity” with a practice that was also common during episodes of severe air pollution, Mr. De Kai said.
“It was a big reminder to people that masks are important not only to protect yourself from the pollution but also to avoid infecting those around you,” he said.
In Taiwan, SARS and recent air pollution were the two main factors that prompted people there to develop the habit of mask wearing, said Yeh Ming-Jui, a professor of public health at National Taiwan University in Taipei.
Professor Yeh said he believed mask wearing was not more widespread in the West because people there had no immediate memories of a severe pandemic — at least until now.
“The experience and health practices of past generations have been gradually forgotten,” he said.
Amy Chang Chien contributed reporting from Taipei.