MARY LOUISE KELLY, HOST:

Right now is a brutal time for hospitals that care for children. A surge of respiratory illnesses is swamping emergency departments nationwide, much of it due to the viral illness known as RSV. NPR's Will Stone visited one hospital in Washington state.

WILL STONE, BYLINE: It's noon in the emergency department at Seattle Children's Hospital. But Dr. Tony Woodward says it already feels like the evening rush.

TONY WOODWARD: So to have a nighttime or evening volume at this time of the day means things are just going to get tremendously worse as the day goes on.

W STONE: Woodward is the medical director of the emergency department. He says it's at nearly 200% capacity. And you can tell the moment you step through the main entrance.

WOODWARD: Now we're walking into our main lobby, which is not meant to staff - to have a lot of patients.

W STONE: It's filled with parents wearing masks, sick children at their side. Everywhere we go, it's more of that. By the elevator...

WOODWARD: We have another 15 patients.

W STONE: Even an old storeroom is serving as a place to keep patients.

WOODWARD: As you can see, we've used every possible space to try to put patients.

W STONE: The entire hospital is backed up. Woodward says about a third of the patients in the emergency department are stuck waiting for an inpatient bed.

WOODWARD: And then we don't have the beds available to take care of the patients from the waiting room. So we see them in a waiting room. We see them wherever we can put them in a corner.

W STONE: This early and intense wave of respiratory illness is unlike anything Seattle Children's Hospital has dealt with before. Last week, the emergency department had its busiest day ever.

KIM STONE: We're on track to beat that today.

W STONE: That's Dr. Kim Stone.

K STONE: At any given time, about 50% of our patient population is here with some sort of infectious symptom that may be attributable to RSV. There's also several other viruses circulating right now.

W STONE: RSV - it's a common viral infection that leads to a mild cold for most people. But for young children, it can be very serious, even life-threatening. Stone says they typically see this kind of surge later in the year.

K STONE: We're not even at the peak. And so we're expecting it's going to remain like this through the early winter months. And we don't know for how long.

W STONE: It's not just RSV making her nervous. She says the flu hasn't made much of an impact yet, raising the possibility that just as RSV calms down, flu could hit hard. Experts say this bad season is largely a legacy of the pandemic. Because of COVID precautions, young children didn't have as much exposure to common viruses.

K STONE: You have sort of more naive immune systems that are now being affected by all of the viruses that are circulating. So you're going to get more patients that are getting sick and transmitting it. Back to school, no masks - we're not doing the social distancing, all of those things.

W STONE: This wasn't a complete surprise. For example, Rachel Baker, an epidemiologist at Brown University, had modeled how pandemic measures could lead to a scenario like this.

RACHEL BAKER: What we're seeing now is just all those cases that would have happened distributed over multiple years happening at one point.

W STONE: While there's still quite a bit of uncertainty, Baker says she doesn't expect the RSV season will stay this intense through the winter months.

BAKER: It's taking off. It's spreading really well. It's transmitting through the susceptible population. So it's unlikely that that spike is going to hang around for many months.

W STONE: And she says a child who gets RSV isn't likely to get sick from it again a few months later, though unlike flu, there is no vaccine available for RSV yet. The surge of pediatric illness comes as health care is dealing with staffing shortages. Despite the crush of patients, standing on the floor of the emergency department feels relatively calm. But Dr. Tony Woodward says it's hard to see families waiting so long, sometimes only to give up.

WOODWARD: They've waited for two or 3 hours and said, you know, I've had it. I'm going home. And we try to keep track of those, make sure their PCPs are aware of that. But it's really disheartening to us because that's not the way we want to practice.

W STONE: He says children's hospitals had a reprieve during much of the pandemic. Now it's shaping up to be a long, grueling winter. Will Stone, NPR News. Transcript provided by NPR, Copyright NPR.