Two childhood viruses at near zero, a ‘good side effect of COVID-19,’ a Utah pediatrician says

But RSV, which mostly strikes infants and toddlers, is likely to ‘come roaring back,’ doctor says.

(Photo courtesy of Intermountain Healthcare) Dr. Andrew Pavia, director of epidemiology at Intermountain Primary Children's Hospital and chief of pediatric infectious diseases at University of Utah Health.

Two diseases that usually hit children hard in the winter — pediatric flu and RSV — are practically nonexistent this year because of the COVID-19 pandemic, a leading Utah pediatrician says.

The bad news: Both could come back with a vengeance next year.

At Intermountain Primary Children’s Hospital, doctors have not hospitalized any children with RSV this season — and only one child in Utah has been hospitalized with the flu, said Dr. Andrew Pavia, director of epidemiology at Primary Children’s and chief of pediatric infectious diseases at University of Utah Health.

Most years, Pavia said, 80 children a week would be admitted to Primary Children’s with RSV, with a third of them needing to go into the intensive care unit.

As for the flu, Pavia said, the federal Centers for Disease Control and Prevention has reported about 1,400 cases of pediatric flu nationwide — when, in an average year, “that number would be in the 500,000 range,” he said.

“We’re seeing something that I have never seen in the last 35 years,” Pavia said Monday during Intermountain Healthcare’s weekly community coronavirus briefing on Facebook Live. “It’s really, truly, one of the good side effects, if you will, of the COVID-19 pandemic.”

Some of the decline in the flu may be credited to COVID-19 travel restrictions, Pavia said, since flu strains are usually carried by people traveling from other countries. Pavia added that masks, hand-washing and social distancing are known to dampen the spread of the flu — and taking those public health measures for COVID-19 is “a natural experiment where we’re controlling [the flu] really dramatically,” Pavia said.

The drop in RSV, which stands for respiratory syncytial virus, “is somewhat more perplexing,” Pavia said. A major symptom of RSV is a runny nose, and nasal secretions are a prime way the virus spreads — so masks and hand-washing are likely limiting how much those secretions get around.

Kids under age 3, who are most susceptible to RSV, are not congregating as much during the pandemic, with fewer play dates and day care visits, Pavia said. He also noted that older siblings who are learning online or having fewer in-person school days aren’t bringing as many viruses home.

All that explains why RSV numbers would drop, Pavia said, but not why “it’s practically zero across the nation.”

One theory experts are discussing, though there’s not a lot of evidence to support it yet, Pavia said, “is that viruses interfere with each other. And when one virus dominates the jungle, it forces all the other animals out, essentially. … Viruses have these weird interplays that we don’t fully understand.”

Those low rates of flu and RSV aren’t likely to last into next year, Pavia said.

“It’s very likely that when both flu and RSV have been away for a while, you’ll have more people fully susceptible to it,” Pavia said. “So when it arrives, it spreads more dramatically and we see more severe disease.”

Flu rates tend to oscillate, Pavia said, with a mild year often followed by a severe one. RSV, on the other hand, “depends a lot on, every year, having a new crop of babies who are completely susceptible to RSV. In Utah, that’s another 50,000 good hosts for the virus to attack. This year, we’re going to have a whole year of infants who never saw RSV. So next year, we’ll have twice as many naive infants who are susceptible to it.”

Doctors in Western Australia, Pavia said, noticed that RSV was largely absent there in June and July — when it’s winter in the southern hemisphere — while the country brought its COVID-19 spread under control. Recently, as COVID-19 restrictions have been loosened there, doctors saw a huge surge of RSV during the Australian summer.

“RSV’s going to do something really strange when it comes back,” Pavia said. “We really can’t predict it very well. Our gut feeling is that it will come roaring back, and we’ll have a bad RSV year when it does return.”