5 big reasons why kids are getting sick and flooding ERs — and 'immunity debt' isn't one of them

• There are multiple reasons why so many kids are sick right now.
• The idea of an immune "debt" isn't quite accurate — childrens' immune systems are fine.

Children with viral illnesses including RSV, flu, and COVID-19 are flooding ERs and urgent care centers. Federal labor data shows a record number of parents in the US have been skipping work this fall to take care of sick kids.

Doctors, nurses, and epidemiologists say there are several things at play contributing to the big viral soup — and they are wary of dismissing it with any one simple explanation, like "immunity debt."

Over the past two years, the term "immunity debt," a phrase which was never previously used in scientific literature, has taken off. In academic position papers, on TV, and even in PediaSure pamphlets, "immunity debt" has quickly become a catchall phrase used to suggest that some kind of "gap" in infections brought on by pandemic masking and isolating is to blame for the current wave of respiratory illnesses.

But in conversations with eight leading infectious disease experts, Insider found five complex and interwoven factors that may be driving the viral trends — and none can be easily summed up as an immune deficit.

We are testing for, and paying attention to, RSV more than we ever have before

Ask any doctor, nurse, or public health expert and they'll tell you: one key reason we're seeing more RSV this year is because providers are looking for it.

"We're definitely testing for RSV more than we used to," pediatrician Manuela Murray, medical director of the Pediatric Urgent Care Centers at the University of Texas Medical Branch, told Insider. "Before the pandemic, even though the test for RSV was available, we didn't use it that much," largely because "knowing that it's RSV is really not going to change anything that we do."

There is no specific medicine that can treat RSV, and no vaccine yet either.

When COVID came along, viral testing became more ubiquitous.

"Perhaps there were a lot of kids out there in previous years, years prior to the pandemic, that had RSV — we just didn't know," Murray said.

RSV has always been a bad illness for little kids and older people. It's especially dangerous for newborns under six months old, whose tiny airways can quickly become obstructed with mucus and inflammation.

RSV has long been "the number one cause of hospitalization for infants," Dr. Pedro Piedra, a professor of molecular virology and pediatrics at Baylor College of Medicine, told Insider. "That has not changed."

The pandemic threw off RSV's typical seasonality patterns

RSV usually surges in December, January, and February, but it hasn't done that since the pandemic began.

In 2021, "we saw RSV in the summer, which is totally off," Murray said.

Dr. Meredith McMorrow, a medical officer in the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases, says RSV rates were 30% higher than usual for kids under five years old in 2021. People just didn't notice, because the season was spread out on a low "simmer" from July 2021 until January 2022.

"Because it was such a long season for us, it never caused the alarm and everything that this season has provoked," she told Insider.

The good news, McMorrow said, is that much of the US appears to be turning a corner with RSV. The South looks like it's just past the peak, and Midwest and Mid-Atlantic states both appear to be peaking now.

Kids are living in a 'hot fire' of viruses again

The current illness wave is also a result of more schools, daycares, and offices reopening, masks coming off, and people intermingling more than they did at the height of the pandemic, before vaccines were available.

But fewer masks and less distance doesn't totally explain the current trends.

"Florida, Texas, countries such as Sweden that really had public health measures in place for a very short duration of time, they are also seeing similar surges," doctoral public health student and pharmacologist Sabina Vohra-Miller, founder of the blog "Unambiguous Science," told Insider.

No matter when kids enter daycare or school, they generally suffer through "two years of getting sick," Murray said. This has always been true, but the pandemic made the issue more universal by bringing together kids of all ages at once.

Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University Medical Center, says there is an "exposure debt" at work, not an immunity debt.

While it is true that people avoided getting many viral illnesses during the darkest days of the pandemic, that doesn't mean that our immune systems are carrying a "debt" or have been degraded to the point where they can't effectively manage new infections anymore.

"Childrens' immune systems are just fine," Schaffner said during a recent Infectious Diseases Society of America press briefing. "Now that they're exposed, they're having to deal with this virus, and the virus has many more opportunities to spread."

Piedra thinks about the way that viruses are recirculating "kind of like putting kerosene on wood — you have a very hot fire."

But the current wave of illness is not a sign that toddlers should have been exposed to their peers' pathogens earlier on in life, or that we made an error by not letting them get sick.

Infants who are exposed to RSV at a very early age are at higher risk of both short-term and long-term complications of RSV infections, like asthma. Because infants don't generally develop good defenses against RSV until after their second or third infection, they can suffer multiple hospitalizations.

"There is no advantage for a young child, a young baby, to be exposed to RSV at an early age," Vohra-Miller said.

Her newborn son was rushed to the hospital with RSV once in 2017, at the age of 10 weeks old, and then again less than two years later, with the exact same illness.

"The idea that our poor immune system is going to sit there and atrophy because we weren't exposed to RSV in infancy, I find that completely laughable," she said.

Even after childhood, immunity to RSV is still transient, and it's possible (though rare) to get sick with RSV twice in one season.

"People shouldn't be upset that they didn't get it last year, they should be thrilled," Dr. Aaron Glatt, an infectious disease expert who chairs the Department of Medicine at Mount Sinai South Nassau, told Insider.

In 2021, health authorities in Stockholm, Sweden, even recommended parents keep their young kids home from preschool if they had newborns in the house, just to avoid bringing a potentially devastating case of RSV home.

Vaccines against RSV are in the pipeline with federal regulators, and may be available for pregnant people and older adults late next year. It's possible that shots for toddlers may not be far behind.

Until then, research suggests nearly every kid in the US will get infected with RSV at some point before their second birthday.

There is an overall lack of capacity in hospitals

There is a lack of capacity for all kinds of sick people in hospitals right now, but especially kids. Responding to higher demand for COVID patients and mental health issues, hospitals have been shutting down pediatric ICUs, and reducing the number of beds reserved for children and expectant mothers.

"I'm really worried about our healthcare systems," public health expert Katelyn Jetelina, author of the popular "Your Local Epidemiologist" newsletter, told Insider.

Part of the reason that there's not enough space for everybody who needs care is because healthcare workers quit in droves during the pandemic due to the burnout that comes from long hours, low pay, and even workplace violence.

"Beds are still closed, and they're closed due to lack of staff," registered nurse Martha Kuhl, secretary-treasurer of National Nurses United, told Insider, referencing UCSF Benioff Children's Hospital in Oakland, California, where she worked until September. "Unfortunately, every unit in the hospital is very, very short staffed."

COVID infections may have messed with kids' immune systems

Many public health experts believe young children who recently had COVID may also be more sensitive and susceptible to viruses right now. This idea is called "immune dysregulation" or dysfunction, and it's a phenomenon that can be triggered by various infections — not just COVID.

Recent research suggests people who've had even mild COVID may experience this kind of susceptibility for a period of about eight months after infection. It's not a stretch to imagine the millions of small children across the US who recently had Omicron infections might be more vulnerable than usual to RSV or the flu. It could be one reason why more hospitalized school-age children are presenting with coinfections of multiple viruses at the same time. But the science isn't conclusive.

Whatever the reasons behind our current predicament, the playbook is clear: Vaccinate for illnesses like flu and COVID, wash your hands, keep newborns away from sick people, and remember to exercise and eat right to keep your immune system humming along.

"If you get less respiratory diseases, your body will be healthier," Piedra said. "These viruses, whether they be influenza, or RSV, or human metapneumovirus, can have a significant consequence on our health."