School Re-Openings May Bring a Spike in Common Cold Cases

Child at school during COVID-19 pandemic.

Vladimir Vladimirov / Getty Images

Key Takeaways

  • Hong Kong saw a burst of common cold infections when schools re-opened this fall, even with COVID-19 safety precautions in place.
  • The illness appears to be driven by rhinovirus infection—a respiratory virus that transmits readily on surfaces.
  • It’s possible that communities in the U.S. will see similarly high cases of the cold as schools begin to re-open.

As schools in the U.S. make plans to re-open in COVID-19-safe ways, they may have to contend with another, unexpected, respiratory illness—the common cold.

The warning comes from Hong Kong, where researchers reported a spike in common cold cases as students there returned to in-person learning, per a February study published in Emerging Infectious Diseases, the journal published by the Centers for Disease Control and Prevention (CDC).

The authors say it may indicate what’s to come in the U.S. and the rest of the world as children gather for in-person classes.

In Hong Kong, schools were dismissed between late January and late May 2020, and again between July and September. Schools were allowed to re-open in October, provided they followed COVID-19 prevention measures including mandatory mask-wearing, extra spacing between desks, increased ventilation, and hand washing. And yet, within the first few weeks, the authors report there were almost seven times more large outbreaks of upper respiratory tract infections among school-aged children than in 2017, 2018, and 2019 combined.

“It was kind of a surprise that all those measures weren't able to stop the common cold from spreading,” one of the study's authors Benjamin Cowling, BSc, PhD, FFPH, a professor of epidemiology and biostatistics at Hong Kong University, tells Verywell. “Pretty much everything that you could think of, we did in Hong Kong, and it wasn't enough to stop these common colds.”

What This Means For You

Scientists aren’t sure exactly why some viruses that cause the common cold are resilient to COVID-19 prevention measures. Experts recommend encouraging kids to practice good handwashing, especially before eating, and ensuring that surfaces remain as clean as possible to try and mitigate the spread in schools. But there's no need to worry—if your child does catch a cold at school, it likely won't be serious.

What Caused the Outbreaks

Mere weeks after reintroduction to in-person settings, schools in Hong Kong reported 482 outbreaks, despite following strict COVID-19 precaution measures. Most of these were in primary schools and nurseries, with a small portion of outbreaks in secondary schools.

An outbreak was defined as at least three students per class developing at least two symptoms of upper respiratory tract infection within four days.

“It is very unusual for schools to be closed or dismissed in response to outbreaks of common colds,” the study’s authors write. Because the symptoms of the common cold are difficult to distinguish from COVID-19, there was a higher strain on laboratories in Hong Kong as they tested those who were experiencing symptoms. The younger children were again dismissed from school.

Scientists aren’t completely sure why these outbreaks occurred. It's possible, Cowling says, that with an increased awareness of respiratory illnesses during the pandemic, more people are reporting their symptoms and getting tested than in previous years. 

Still, such a large increase in cases and hospitalization rates came as a surprise. One theory is that, after many months of social distancing, the children did not have strengthened immune responses that usually come from exposure to pathogens. When they returned to the classroom, they were introduced to a slew of new respiratory viruses.

Developing Immunity

Throughout the COVID-19 pandemic, there has been a notable decline in the spread of respiratory viruses, like influenza and respiratory syncytial virus (RSV). For example, there have only been about 1,400 cases of the flu in the U.S. this year so far, compared with more than 174,000 positive cases at this time last year.

The outbreaks observed in Hong Kong schools and childcare centers were likely caused by rhinovirus, a virus that leads to the more mild common cold. A report published in The Lancet in October noted a similar uptick in rhinovirus cases immediately following the opening of schools.

There are hundreds of different strains of rhinovirus. When someone is exposed to one strain, their body may mount a better immune response when introduced to a different strain, though it won’t likely be completely protected. When children, especially young ones with underdeveloped immune systems, are exposed to more strains of the virus, their bodies may learn to defend against new ones.

Children who have been social distancing may be missing out on exposure to pathogens in a formative time in the development process of their immune system. “Children who have been out of school for a year—if they age four or five or six—that's really missing a substantial fraction of their life,” Cowling says.

Research indicates that SARS-CoV-2, the virus that causes COVID-19, primarily spreads via respiratory droplets. Rhinoviruses similarly spread through airborne transmission, but can also live on surfaces and can transfer quite well between a table and hand, for instance.

Why Aren't COVID-19 Precautions Preventing Outbreaks?

In a study published in the journal Nature last year, Cowling and his colleagues reported that face masks were effective in quelling the spread of influenza and coronaviruses. But they appeared ineffective in preventing rhinovirus transmission, and scientists aren’t quite sure why.

“Schools are a place of congregation and even though children are trying their best and they're wearing masks and washing their hands, they still are touching surfaces,” Janet Englund, MD, professor of pediatric infectious diseases at the University of Washington and Seattle Children’s Hospital, tells Verywell. “They are going to touch their eyes, pick their nose, rub their face, and those viruses are likely to persist on surfaces for at least a little while.”

Englund says that the transmission of respiratory viruses is practically inevitable when a group of children congregates. Maintaining good hygiene measures should help prevent some spread of respiratory viruses.

For young children who are particularly susceptible to illness, exposure at schools may lead to more infection. However, if children have the time to grow in a more sheltered environment before being exposed to school, their bodies may be more able to fend against mild infections.

“As kids get older, their bodies are a little bit hardier and a little more resilient to those viruses that don't normally cause severe infection,” Aaron Milstone, MD, MHS, associate professor of pediatrics and epidemiology at Johns Hopkins University, tells Verywell.

What This May Mean for the U.S.

Cowling says that in Hong Kong, scientists and officials did “pretty much everything” they could think of to limit the spread of respiratory viruses when creating COVID-19 prevention measures. And yet, the viruses that cause the common cold alluded them.

“We think is quite possible other parts of the world will have the same experience when schools go back after long periods of absences for the same reasons that the children have lost some of their immunity to these infections,” Cowling says.

The outbreaks didn’t appear to reach their peak before Hong Kong officials chose to shut down schools in November. So, there may be no way to know whether the population could have reached any level of increased herd immunity if schools had remained open.

But the severity of the outbreak may depend on how communities are handling COVID-19 safety measures. “If people don't expect to see COVID in their community, they might not be wearing masks and practicing the same COVID precautions that other places are where there is more COVID,” Milstone says.

Unlike typical years, when people may be more likely to shrug off a cold and return to work or school, people now may be much more cautious of symptoms of respiratory illness. If adults are becoming infected by school-going children in their circles, they may be less likely to return to life as normal.  

“If suddenly there's a lot of children and their parents getting sick with common colds, that's going to mean a lot of people on sick leave, and that's going to be disruptive to communities,” Cowling says.

Staying Safe

Englund says there’s no feasible way to allow students to come back to school without some degree of congregation. And while no method to prevent transmission is likely to be perfect, she says that encouraging hand washing and making hand sanitizer available is a step in the right direction. And if you do experience symptoms, it’s best to play it safe.

“If you're sick please stay home—don't go to work, don't go to school, maybe don't even go to the grocery store for a day or two,” Englund says. Even with precautions in place, however, some illnesses may be unavoidable as people begin to interact more closely in the coming months.

“But exposure to germs is normal and, I think people are seeing it's not always an “if,” it's a “when,’” Milstone says. “Just try to do those basic things like wash your hands and not be around other people when they're sick.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Poole S, Brendish N, Tanner A, Clark T. Physical distancing in schools for SARS-CoV-2 and the resurgence of rhinovirusLancet Resp Med. 2020;8(12):e92-e93. doi:10.1016/s2213-2600(20)30502-6

  3. Leung N, Chu D, Shiu E et al. Respiratory virus shedding in exhaled breath and efficacy of face masksNat Med. 2020;26(5):676-680. doi:10.1038/s41591-020-0843-2

By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.