During the 2020-21 school year, non-COVID respiratory viruses were mercifully mostly absent.
But with more aspects of society opening up and some districts choosing to forgo masks despite CDC’s recommendation for universal masking in school settings (opens in new tab), the potential exists for other viruses to come back with a vengeance alongside the Delta variant this school year. These viruses include common colds, the flu, and RSV, a respiratory virus that can cause severe symptoms in young children that has seen an unusual summer surge (opens in new tab) in the U.S. this year.
“We had incredibly low rates of influenza, and other diseases caused by pathogens other than SARS-CoV-2. Those are all going to come back, and they may come back with a vengeance,” says Dr. Albert Ko, an epidemiologist at the Yale School of Public Health.
Why Were Non-COVID Seasonal Virus Levels So Low Last Year?
The first part of this answer is obvious: mitigation efforts from masking to social distancing limited the spread of these viruses, both within schools and beyond.
But there may be additional factors at play, including SARS-CoV-2 establishing dominance. “I think there's also probably a little bit of virus-virus battling going on in the past 18 months as well, where the circulation of the coronavirus has probably also helped keep flu and some of these other respiratory viruses out,” says Dr. Richard Webby, a virologist at the St. Jude Children’s Research Hospital who specializes in flu research (opens in new tab). “In a year where you have a bit of say, RSV and flu activity, or even flu A and flu B, typically peaks of activity within a country don't overlap. So they squeeze out their own niches within sort of their winter season. And we don't really understand exactly how that works.”
He adds, “Certainly social distancing and mask wearing seemed to play a role. But these viruses went away everywhere. So they went away in countries that didn't do that very well. They went away in countries that did do that well.”
What Will Non-COVID Viruses Be Like This Year?
Dr. Gigi Kwik Gronvall, an immunologist at the Johns Hopkins Bloomberg School of Public Health, says some people are using the phrase “immunity debt” to describe the coming year because so few children got respiratory viruses last year. “I don't really like that term, because it implies that we're predestined to get these diseases,” she says. “But it does have the potential to be a pretty bad year for RSV and a pretty bad year for colds. Is it going to be a bad year for flu? I think the jury's still out.”
Some are predicting lots of flu activity this year while others believe we may forestall a bad flu outbreak for at least one more season, she says.
Webby worries about RSV because children normally get infected in their first year or two of life and then might develop some immunity, but that hasn’t happened the past 18 months. Similarly, about 20 percent of the population gets infected with the flu each year, Webby says, and get some level of immunity the following season as a result. It’s unclear how taking that immunity off the board might impact this flu season.
“We haven’t been in this situation before,” Webby says. “What happens when nobody gets infected with flu for two seasons in a row? What does the history book say? The history books don't mention anything like this.”
How To Limit Spread and Keep Kids in School
The COVID-prevention playbook of distancing, hand hygiene, and vaccination when available, also applies for non-COVID respiratory viruses. “Some of the measures that I hope that schools are still going to put into place and keep in place for COVID will help with some of these diseases,” Gronvall says. “For example, if they invested in getting a HEPA filter device, a portable device to put in classrooms, which was something that they can use their flexible funds for, that will help with the spread of flu as well as other airborne viruses.”
She adds, “A lot of people seem to think that there's sort of like a ‘no pain, no gain’ approach when it comes to infectious diseases. And that's just not true. It's really better to go through life not getting any. There's no advantage in getting it except then maybe you won't get that one particular one again, but there are plenty of others.”
As always, it’s a good idea to stay home when you have symptoms, health experts say. However, with the increased emphasis most districts are placing on in-person school this year, it may not be realistic to have students quarantine with the common cold. “In schools when somebody comes in with a cough or a fever, or a headache, or runny nose, it may or may not be COVID,” Ko says. “The school systems are going to have to tease that out. And who gets sent home, who needs to get tested, how they're going to test them efficiently, that’s going to be another challenge.”
The CDC has announced (opens in new tab) it will be replacing PCR tests with a new test that will check for both COVID and the flu at the same time, which can help public health authorities better track both viruses.
"The good thing is that we've learned a lot," Ko says. "A year and a half ago, we had no tests. And now we're doing a lot of testing for COVID. It has become part of our routine life. So I think there are ways, of course, to deal with this.”
- CDC Reverses Course: Masks Now Required for Vaccinated Educators and Students in Schools (opens in new tab)
- The Delta Variant: Should Educators & Parents Be Worried? (opens in new tab)