As soon as Americans return to crowded offices, schools, buses, and trains, so too will their sneezes and runny nose.

After some Americans were introduced to the idea of ​​wearing masks to protect themselves and others, they are now considering a behavior that is rarely seen in the US but has long been a fixture in other cultures: routinely a mask To wear when symptoms of a cold or flu occur Even in a future where Covid-19 is not a major concern.

“I will continue to feel obliged to protect others from my illness if I have a cold or bronchitis or the like,” said Gwydion Suilebhan, Washington writer and art administrator who plans to fly in airplanes in situations like wearing masks. “It is a responsible part of a person in a civil society to take care of the people around you.”

Such routine use of masks has been common in other countries, especially East Asia, for decades to protect them from allergies or pollution, or to protect people nearby.

But until the coronavirus crisis, there was rarely a cultural boost to practice in the United States and several other Western countries. Although masks have been shown to be effective in mitigating the transmission of Covid-19, they now hold weight as symbols in the cultural wars between red and blue, with parts of the country viewing them as an affront to their freedoms and others as a show of care consider others.

Dr. Anthony S. Fauci, the director of the National Institute for Allergies and Infectious Diseases, pondered the future of masking this week. “It is conceivable that in a year or two or more, during certain seasonal periods when you have respiratory viruses like the flu, people might actually wear masks to reduce the chances of you spreading it these respiratory diseases, ”he said on Sunday at“ Meet the Press ”.

However, other leading American health officials have not encouraged the behavior. The Centers for Disease Control and Prevention, which advised against wearing masks at the start of the pandemic and didn’t change their guidelines until a few months later, don’t advise people with flu symptoms to wear masks and say they “may not be effective in restricting Transmission in the community. “

This is partly because there is no proper scientific consensus on the effects of masks on influenza virus transmission, according to experts who studied this.

Nancy Leung, an epidemiologist at the University of Hong Kong, said the science studying possible links between masking and the emission or transmission of influenza viruses is nuanced – and that the nuances are often lost in public.

Dr. Leung said the strongest evidence of a link came from studies showing how surgical masks reduced the amount of influenza virus an infected person emitted, an effect epidemiologists refer to as “source control”. These studies showed that the masking was particularly effective in stopping the emission of influenza droplets, she added.

Measuring the impact of wearing surgical masks on the transmission of influenza in the community has been more complicated, she said.

So far, according to Dr. Leung, there was no clear evidence from randomized controlled trials – the gold standard in scientific research – that masking decreased the transmission of influenza virus in a community.

There was some evidence from observational studies that masks reduced influenza virus transmission in the community, but that the research had one caveat: observational studies cannot isolate masking from other possible factors such as hand hygiene or social distancing.

“It’s hard to decipher whether or not this observed reduction in transmission is due to face masks alone,” said Dr. Leung.

For similar reasons, the fact that the flu all but disappeared in the US during the coronavirus pandemic – and that many Americans have anecdotally reported that they caught fewer colds than usual in 2020 – isn’t just evidence that masks did were responsible.

Updated

May 13, 2021, 6:20 p.m. ET

In East Asia, the historical use of masks is not based solely on 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 the pandemic affects people as a group, wearing a mask is a way to lessen the individual’s impact on others.”

De Kai, a computer science professor at Hong Kong University of Science and Technology who has studied masking etiquette, said that for people in Chinese territory and elsewhere in East Asia not wearing a mask while sick would be roughly equivalent to a person are. “Sneeze all over the subway” without covering your nose in an American city.

“Of course nothing is black and white,” he added. “Of course it’s a question of degree. But there is a difference between East Asian cultures and very, very libertarian US culture. “

(As 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, introduced during times of social unrest to curb violence.

For example, New York State passed an anti-masking law in 1845 to prevent tenants from demanding land reform. This comes from research by Sharrona Pearl, a professor of medical ethics at Drexel University in Philadelphia. During the 1920s through 1950s, several states passed similar laws in response to the violence of the Ku Klux Klan.

Several East Asian scientists said in interviews that the region’s customs regarding wearing masks are very different, as people in each country have responded to different epidemiological or environmental threats over the years.

Jaehwan Hyun, a professor of history at Pusan ​​National University in South Korea, said ignoring the nuances could be dangerous.

“It enforces the idea of ​​an Asian as a single race that maintains a single mask-wearing culture,” said Hyun. “I think this is an easy way to develop discriminatory or racist arguments against Asians.”

In 19th century Japan, some people wore British-made respirators to protect themselves from colds, coughs and respiratory diseases, said Tomohisa Sumida, visiting researcher at Keio University. Wearing masks became common after the pandemic influenza of 1918 and again when many people there suffered 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, Hyun said. Masking was also common in the South Korean capital, Seoul, in the 1980s due to factory-induced air pollution and the tear gas that accompanied protests against authoritarian rule.

However, according to Hyun, regular masking wasn’t common in the country until the mid-2000s when the government recommended the use of an N95-like mask to protect against the seasonal dust storms that invade the country from Mongolia and northern China.

“In general, until recently, Koreans believed that wearing masks was a kind 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 this coronavirus helped create a “cultural familiarity” with a practice that was common during episodes of severe air pollution, Mr. De Kai said.

“It was a great reminder for people that masks are important not only to protect themselves from pollution, but also to prevent people from getting infected around you,” he said.

In Taiwan, SARS and recent air pollution were the two main factors that led people there to develop the mask-wearing habit, said Yeh Ming-Jui, a public health professor at National Taiwan University in Taipei.

Professor Yeh said he believes wearing masks is not more common in the West because people there have no immediate memories of a major pandemic – at least until now.

“The experiences and health practices of past generations have been gradually forgotten,” he said.

Amy Chang Chien contributed to coverage from Taipei.