COVID-19 Is More Severe When Kids Have Secondary Viral Infection

A study shows that COVID-19 patients under 5 had worse symptoms if they also had RSV or the flu. While this isn't surprising, the information does help us understand why it's been such a rough sick season.

Toddler sleeping in hospital bed with oxygen

Jill Lehmann Photography/Getty Images

A new study confirms what parents and pediatric healthcare providers likely already know: Children with COVID-19 and another infection, such as RSV, are more likely to be hospitalized than their peers with COVID-19 alone.

The study, which will appear in the February 2023 issue of Pediatrics, published online on January 18. It looked at more than 4,300 U.S. children hospitalized with COVID-19 from March 2020 to February 2022. It found that pediatric COVID-19 patients under 5 were significantly more likely to have severe respiratory illness if they also had another virus like rhinovirus or enterovirus.

"This research confirms what many of us have observed," says Dr. Mark Kline, physician-in-chief and chief academic officer at Children's Hospital of New Orleans. "Over the past year, more and more children hospitalized with COVID-19 have been co-infected with one or more other viruses, including RSV, influenza, and rhinovirus/enterovirus."

The news may not come as a surprise to Kline—or parents. But it might feel like another troubling headline during a challenging season that has included a "tripledemic" of COVID-19, RSV, and flu cases, according to experts, including White House COVID-19 response coordinator Ashish Jha.

What does the new research tell us, and what should weary parents do with it? A trio of experts weigh in.

Why Are Children Getting Multiple Viruses at Once?

COVID-19, the flu, and RSV are all highly infectious, explains Dr. Michael Harris, M.D., a pediatric emergency room physician with Northwell Health's Cohen's Children Medical Center of New York.

People of any age can get them, but children's social and academic lives put them at an increased risk.

"Kids tend to have more contact with other kids than adults," Dr. Harris says. "They're in daycare and school. They play contact sports."

Children have also had less exposure to viruses over the course of their lives, so their immune systems are often weaker. And they are even more susceptible to another infection when they are sick because their immune system is compromised as it tries to fight off one virus, Dr. Sharon Nachman, M.D., the chief of the division of pediatric infectious diseases at Stony Brook Children's Hospital.

Finally, Dr. Nachman says many children were not exposed to typical viruses, like the flu and RSV, because of COVID-19-related school and daycare closures and reduced socializing. As a result, the immune system hasn't been "taught" how to fight these viruses, so more kids are getting sick with multiple ones at once.

"Those viruses never went away. We just weren't getting them because [we weren't seeing one another]," Dr. Nachman says.

Does This Study Show Why Sick Season Feels Worse This Year?

The study is from March 2020 to February 2022, but could it explain why nearly half of parents said their kid had already been sick by October? Or why the CDC released a health advisory about increased respiratory activity, particularly among children, in early November?

Experts think so.

"It's certainly one reason that we've seen a surge in hospitalizations for respiratory illness over the past several months," Dr. Kline says.

Dr. Nachman also points out that precautions, such as masking and social distancing, helped stymie the flu and RSV for the last two years. With people returning to pre-pandemic habits, there's more risk for illness.

"We did such a good job protecting everybody for a good reason…now, we're not protecting everybody," Dr. Nachman says. "Now, no one is masking."

When Should You Take Your Child to the ER?

Dr. Harris says the surge of pediatric admissions for respiratory illness has tapered off in recent weeks and hopes it stays that way. But it's important for parents to understand when to take their child to the ER for further evaluation. Dr. Nachman and Dr. Harris say that a high fever alone is typically not a reason to take a child to the ER—unless otherwise noted for health reasons by your child's provider.

Dr. Nachman says to look for trouble breathing.

"If you take a kids' shirt off, and you see that space between the ribs as sucking in and out and in and out, they are having trouble breathing," she says.

Dr. Nachman says a reduced appetite is typically normal, but refusal to drink or poor diaper output is a flag. If in doubt, trust your gut.

"I tell parents, 'You are my best detective. You know what your child looks like when they are mildly sick, and you know what you feel like when they are really sick. If you feel you need to talk to me on the phone, call me,'" Dr. Nachman says.

Dr. Michael Harris

"I think we have to follow common sense that we should have been following for the last 20 years. If your children are sick, keep them home."

— Dr. Michael Harris

How To Protect Your Kids

As cold/flu/RSV season hopefully wages on, there are ways parents can take steps to protect their kids. First, Dr. Nachman suggests going back to basics.

"Good eating habits—water, vegetables, and fruit—and good sleep habits are critically important," she says. "It helps the body produce the right hormones at the right time. It helps the body's immune system get tuned up. I recognize it's hard, but the earlier we start those hard tasks, the bigger difference it makes lifelong."

Dr. Harris hopes people keep in mind the fundamental lessons they learned during the pandemic, too.

"I think we have to follow common sense that we should have been following for the last 20 years. If your children are sick, keep them home," Dr. Harris says. "Wearing masks. I know it's become a taboo, but if you are in a highly-populated area like a bus, subway, or on a flight, chances are someone has something you don't want, whether that's COVID, the flu, or a cold—I don't think any of us want any of these viruses."

Finally, Dr. Kline urges parents to vaccinate and boost their children against COVID-19 and flu. Children 6 months and older are eligible for the COVID-19 vaccine and bivalent booster, but CDC data shows a wide variety of vaccination rates for children. Only 2% to 40% of children 6 months to 4 years old have received their first dose, depending on the state.

Even if you take precautions, your child will likely get sick.

"The good news is that every virus your kid is having now does help their immune system become better when they are getting older," Dr. Nachman says. "As much as we would like our children not to have any of these viruses, it is helping their immune system for next time."

Dr. Nachman clarifies that this isn't a reason to forego precautions altogether or have "chicken pox" style parties for respiratory illnesses. But it might help you feel a little less guilty when your kid inevitably brings something home.

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