RSV Hospitalizations Surge, Babies Hit Hardest

Babies under six months old have the highest RSV-related hospitalization rate, data from the Centers for Disease Control and Prevention show, at 145 hospitalizations per 100,000 infants. Infants six to 12 months old were hospitalized at a rate of 63 for every 100,000 children that age. For adults, the hospitalization rate is 0.6 per 100,000 people.

RSV is a common virus that most children encounter by their second birthday. Reinfections can occur at any age. Most people experience mild, cold-like symptoms and recover in a week or two. But RSV can be serious for some infants and older adults, causing bronchitis and pneumonia.

Younger children tend to be at higher risk, in part because their airways are smaller and get more easily clogged when they are inflamed, said Dana Free, a travel nurse with a company called Trustaff, working in a pediatric intensive-care unit in Danville, Pa.

“If you think of it as a straw, and that’s your normal breathing, that’s fine,” Ms. Free said. “You coat it in congestion, essentially snot and mucus, you’re making that airway much smaller.”

Emergency rooms and pediatric hospitals across the U.S. have reported strain due to increased cases of RSV and other common respiratory viruses. Some recent closures of pediatric units have compounded the issue, doctors said, and staff are stretched thin.

Some hospitals in the Northeast are postponing elective surgeries or sending older children to adult hospitals, said Connecticut Department of Public Health Commissioner Manisha Juthani. Those strategies aren’t as effective for pediatric care because fewer children have elective surgeries than adults and hospitalization rates among older children are lower, she said.

Children’s Hospital New Orleans is getting calls from doctors in Mississippi, Alabama and Texas looking for beds for patients, said pediatric infectious disease specialist Mark Kline. “You’re talking about kids who have critical illness because they’re in respiratory failure,” Dr. Kline said. “They’re not occasional calls. It’s every day.”

Schools in states including Kentucky and Ohio temporarily suspended classes or switched to remote learning at least one day this week because students and staff were out sick.

RSV usually spreads from the fall through winter, peaking sometime between late December and mid-February. But with the onset of the Covid-19 pandemic, RSV cases practically disappeared, likely because of Covid-19 mitigation measures including masking that appear to have restricted the spread of a range of viruses.

RSV came back in the summer of 2021, unusual for that time of year, eventually reaching a hospitalization rate of 1.3 per 100,000 people in mid-December. The virus continued circulating this year throughout the spring and summer and surged in recent weeks.

“RSV has done something similar in the previous two seasons where it started early, but nothing to this extent and nothing as widespread as now,” said William Schaffner, medical director at the National Foundation for Infectious Diseases.

Many younger infants might not have been exposed to RSV, in part because of Covid-19 mitigation efforts that kept other viruses in check, doctors said. Mitigation measures have largely been dropped at places including schools and daycare centers, and the relative lack of exposure compared with prior seasons created a wider pool of susceptible people, some public-health experts said.

“This increased number of cases is to be expected, given the number of individuals that are susceptible to the virus at this time,” José Romero, director for the National Center for Immunization and Respiratory Diseases at the CDC, said last week. There aren’t any indications at this time that the cases are more severe, Dr. Romero said.

There aren’t any specific RSV treatments, but some over-the-counter medications can help manage pain and fever, and patients should stay hydrated, doctors said. Most adults and infants without other health conditions don’t need to be hospitalized, the CDC said.

People should seek medical attention if they have trouble breathing, aren’t drinking enough fluids or have worsening symptoms, the CDC said. Some might need additional oxygen, fluids or a breathing tube. Hospitalization tends to last a few days.

Among children under the age of 5, an estimated 100 to 300 RSV-related deaths occur each year in the U.S. while some 6,000 to 10,000 deaths occur among adults 65 and older, according to the CDC. The RSV-hospitalization rate for people 65 and older is per 100,000 people, according to CDC data.

The CDC said it doesn’t have real-time death data because RSV reporting isn’t mandatory.

Areas including the Southeast and South-Central parts of the U.S. last week recorded declines in the proportion of tests positive for RSV, Dr. Romero said. In Connecticut, children’s hospitals reported a stable or slightly lower number of children admitted to the hospital compared with the week prior, the state health department’s Dr. Juthani said.

“I’m hoping that we’ve somewhat plateaued in the Connecticut area,” Dr. Juthani said. “The downside is that flu is taking off.”

Doctors and health officials said they are watching how flu and Covid-19 might collide with RSV trends this winter.  

“We likely have not peaked,” said Amanda Castel, an infectious-disease epidemiologist at the George Washington University Milken Institute School of Public Health.

Write to Brianna Abbott at brianna.abbott@wsj.com