Common colds might spike with in-person learning

Researchers in Hong Kong saw nearly seven times as many outbreaks as 2017-19 combined

When many students in the United States go back to in-person learning this fall, parents and school administrators may have to contend with an unexpected infectious disease problem: more colds than usual.

That’s the caution coming from researchers in Hong Kong, who published a study last week detailing a spike in common colds after students returned to classrooms in the fall following nearly a year of remote learning. Specifically, the researchers reported almost seven times more large outbreaks of acute upper respiratory infections (involving 20 people or more) compared with those recorded in 2017, 2018 and 2019 combined.

“Normally, we don’t think of them as a real public health challenge,” Benjamin Cowling, one of the study’s authors and a public health researcher and biostatistician at the University of Hong Kong School of Public Health, said of common colds. But it can be tough to distinguish the symptoms of a cold from those of COVID-19, especially in kids. And if colds start spreading through schools in the United States, children may be sent home until they have been tested for the coronavirus. They may even have to return to remote learning.

At this point, immunologists can only speculate as to why colds surged after schools reopened in Hong Kong.

What really surprised Cowling was that colds spread despite the strict virus-prevention measures at schools. In Hong Kong, students spend only half a day at school and avoid eating lunch together. They also wear masks all day and sit at distanced desks.

It’s possible that COVID-19 mitigation measures do not work that well for colds. In a study published last April, Cowling and his colleagues found that surgical masks weren’t as effective at blocking rhinoviruses as they were at blocking coronaviruses and influenza viruses. In other words, “maybe the virus can survive the journey through the mask,” Cowling said.

Rhinoviruses are also hardier than coronaviruses because they have strong outer envelopes, which means they can survive on surfaces for longer and can also be difficult to remove from hands.

Some experts say it’s also possible weakened immune systems may have been to blame. Since kids likely had not been exposed to as many colds and other viruses while at home, it’s plausible they could have lost some of their immune defenses, making them especially susceptible to colds when they returned to school.