Two children’s hospitals in the Washington region say they’ve recently seen a large number of children sick with RSV, a seasonal respiratory virus that usually hits during the winter months.

Children’s National Hospital activated surge plans in recent days to respond to the increase, repurposing part of the emergency department for intensive care patients and to use part of the surgical recovery area to provide additional inpatient beds, David Wessel, executive vice president and chief medical officer at Children’s National, said in an interview Wednesday.

Inova Children’s Hospital in Falls Church is also near capacity, largely because of RSV, according to Cynthia Gibson, chair of that hospital’s pediatrics department.

“We are full of RSV,” she said. “We are seeing more RSV now than we normally see in the middle of winter. We didn’t see hardly any last year.”

The virus often presents as a fever, cough and runny nose, but can cause respiratory distress and in severe cases RSV bronchiolitis, causing inflammation of the small airways of the lungs and often labored breathing, doctors said.

The increase in RSV cases appears to be an indirect result of the coronavirus pandemic, public health experts said.

Pediatricians did not see the typical instances of RSV — or other common winter illnesses such as the flu — last winter at the height of the pandemic because there were very few gatherings and near-universal masking. But as coronavirus case numbers dropped in the spring and early summer, emergency orders were lifted and people began to gather again, often without masks, triggering the spread of the illness.

The first cases began to appear in late March at the Northwest D.C. pediatric hospital and have risen steadily over the last 12 weeks, dovetailing with the recent surge in coronavirus cases due to the highly contagious delta variant, Wessel said.

“It’s the rather unusual onset of our winter season that came in the late summer,” he said. “There’s a group of young children who because of the interventions that were made last year to combat covid-19 with respect to social distancing . . . were never exposed to RSV.”

In the 47-bed intensive care unit Tuesday, there were 13 RSV bronchiolitis patients, and an additional six covid-19 patients, as well as children with other illnesses, he said.

The hospital already has surpassed its earlier peak in covid-19 cases due to the delta surge.

There have been as many as 24 children with covid-19-related illnesses in the hospital recently, compared to a previous high of 18 in January. However, Wessel noted, the number was 22 on Tuesday and 17 on Wednesday, a downward trend that he is monitoring closely.

“We know the delta virus is more infectious,” he said. “Most of the children are not vaccinated, so they are functionally a vulnerable population — that’s why we think it’s so important for the people who surround our children to be vaccinated.”

The Virginia Hospital & Healthcare Association on Wednesday launched a statewide ad campaign promoting the coronavirus vaccines amid a spike in infections and hospitalizations, mostly among the unvaccinated.

VHHA is running a video on social media targeted at the vaccine-hesitant and a public service announcement on the radio.

Also Wednesday, the Maryland Department of Health said it received $1.8 million from the Centers for Disease Control and Prevention to pay for community health workers to help boost vaccination rates in Allegany, Dorchester and Somerset counties.

Dan Finkelstein, a pediatrician with Capitol Medical Group in Chevy Chase, said vaccine uptake is high among his patients.

But since school started a few weeks ago, his large practice has been doing a lot of coronavirus testing of children under 12 who are too young to be vaccinated.

“The kids that we’ve had testing positive for covid have almost all been minimally symptomatic. We haven’t had a lot of kids in our practice that have been significantly ill, knock wood,” he said.

Finkelstein said a lot of parents have questions about the connection between the coronavirus and RSV, which is on the rise simply as a function of the on-and-off social distancing of the past year and a half.

“It’s not as though RSV is different or more of a threat than it usually is,” he said. “It’s unusual and unfortunate because hospitals are already struggling to deal with covid patients and now they have to deal with RSV patients at the same time.”

RSV tends to be most severe in children under 2, and typically causes only minimal illness in children 10 or older, he said.

Still, his practice is seeing two to four cases of RSV daily — about half the number it would see in a normal winter.

“But it is noticeably more prevalent,” he said.