Covid-19's omicron variant appears to be affecting children under age 5 in a new way: a harsh, barking cough known as croup.
While croup generally is not harmful, it can be frightening for parents already on edge about their babies and toddlers, too young for the Covid-19 vaccine, becoming infected with the virus.
Doctors say this is most likely occurring because it appears omicron tends to settle higher up in the respiratory tract, rather than deeper in the lungs.
"Little kids' airways are so narrow that it takes far less inflammation to clog them," said Dr. Buddy Creech, a pediatric infectious disease expert and director of the Vanderbilt Vaccine Research Program at the Vanderbilt University Medical Center in Nashville, Tennessee.
When a child with tiny, inflamed airways breathes, it makes a distinctive noise, and can result in a cough that sounds like a dog or a seal.
Creech said that he and his colleagues have noted "croup-like presentations" in young children who test positive for Covid-19. The upper part of kids' airways become very swollen. "When that happens," he said, "there's that characteristic barking cough."
A number of seasonal viruses, including parainfluenza and respiratory syncytial virus, can lead to croup and an infection of the respiratory tract called bronchiolitis. Now it seems, Covid-19 — specifically the omicron variant — should be added to that list.
Dr. Saif Al Qatarneh, a pediatric pulmonologist at West Virginia University, said that he, too, has noted an increase in such diagnoses in tandem with a rise in pediatric Covid cases.
So far, the omicron variant appears to be less severe than the delta variant, Dr. Anthony Fauci said Wednesday during a White House Covid-19 Response Team briefing.
"But remember the caveat: Rapid community spread is seeing larger numbers of children being hospitalized — again, mostly among the unvaccinated," said Fauci, the president’s chief medical adviser.
Al Qatarneh said he and his colleagues are concerned about what may occur in the coming weeks as omicron continues to spread.
"We are still two to three weeks away from the peak of omicron," he said. "The smart thought is to get ready for more patients getting bronchiolitis in children and infants."
A 'bread and butter' diagnosis
One reassuring thought for parents is that croup and bronchiolitis are well-known to doctors, who have had decades of experience treating the conditions.
"Croup is a bread and butter pediatric diagnosis," said Dr. Mark Kline, the physician-in-chief at Children’s Hospital New Orleans. "Infectious croup is one of the first diseases you learn about when you're an intern in pediatrics." Kline's team, too, has noted the uptick in Covid-related croup.
Dr. Amy Edwards, a pediatric infectious disease expert at University Hospitals Rainbow Babies & Children's Hospital in Cleveland, agreed.
"As pediatricians, seeing more kids with croup and bronchiolitis is oddly reassuring," she said, "because we've been dealing with those conditions for our entire careers."
Croup can be "scary to hear, but it doesn't mean there is any problem with the lungs," she said. "The main treatment is to keep the upper airways open and clear until the inflammation subsides."
Croup may require a few days of steroids, but often goes away on its own. Sometimes kids with bronchiolitis need oxygen support or breathing treatments, Edwards said, before generally recovering completely.
Risk for hospitalization as vaccines lag
Edwards and others want to reassure parents that the vast majority of young children with Covid-19 are likely to have mild illness. But it is possible that some children, even previously healthy ones, can develop serious complications that require hospitalization.
On Friday, the CDC released new data showing that hospitalization rates are increasing among the youngest kids for whom there is no vaccine: ages 0 to 4.
More than 4 in 100,000 children under age 5 were admitted to a hospital with Covid-19 as of January 1, the CDC reported.
What's more an NBC News analysis of Health and Human Services data finds that at least 16 states have broken records for the number of pediatric hospitalizations linked to Covid-19.
Nearly 40 percent of the pediatric hospitalizations at Texas Children's Hospital in Houston include children under 5, said Dr. Jim Versalovic, a pathologist who is a co-leader of the hospital's Covid-19 Command Center.
Vaccines are one of the best ways to protect against infection, but those shots are not expected any time soon for the youngest children.
Vanderbilt's Creech, who is also one of the primary researchers for the Moderna KidCOVE clinical trials, predicted a rollout of vaccines for the youngest children no earlier than this summer. Versalovic of Texas Children's, one of the sites for Pfizer-BioNTech's pediatric clinical trials, also said he did not expect any early childhood vaccines until later this year.
The best defense for unvaccinated children, experts said, is to "cocoon" them. That is, surround them with adults and older children who are vaccinated.
"For those who are unvaccinated, this is going to be a rough ride," said Creech. "That may include our young children, and so we really have to protect them as best we can."