The ommicron coronavirus variant caused a spike in cases of potentially serious breathing problems in infants and toddlers, according to a hospital study recently published in the journal Pediatrics.
The study is small and focuses only on COVID-19-related cases at a large children’s hospital in Massachusetts during the pandemic. But it provides some of the first data on the subject and supports anecdotes from health care providers that the latest pandemic variant causes more cases of laryngotracheobronchitis — also called croup — in younger children than previous variants.
In general, croup is a common upper respiratory tract disorder in which significant inflammation and swelling develop in the larynx and windpipe, compromising breathing. Some viral infections usually cause swelling, but allergies and other irritants can also be culprits. Croup can occur at any age, but most commonly affects the small upper airways of infants and young children between the ages of 3 months and 5 years.
Croup gets its name from the characteristic “croupy” cough it causes, which is sometimes described as a seal-like barking cough. Other hallmarks of the condition include a loud, raspy sound when a patient inhales — inspiratory stridor — and respiratory distress.
Before the ommicron wave, COVID-19 was associated with croup in some children, but it did not appear to be a common consequence of the pandemic infection. That changed during the ommicron wave as health care providers reported seeing more cases of COVID-19-related croup in young patients.
While there’s still little data on why that might be the case, experts speculate that early variants and the ancestral SARS-CoV-2 tended to target the lower respiratory tract, leading to more severe disease in older age groups. Meanwhile, Omicron appears to have a predilection for the upper respiratory tract, which may partly explain why it is both more transmissible and associated with relatively milder disease in older age groups.
But in very young children — who have small airways and still not qualify for COVID-19 vaccination — omicron appears to pose a new risk.
Croup cases
In the new study, researchers, led by pediatrician Ryan Brewster of Boston Children’s Hospital, scanned the hospital’s records for COVID-19-related croup cases from March 2020 to January 15, 2022. They found only 75 cases, but 61 of the cases. (81 percent) occurred during the approximately one-and-a-half-month timeframe of the ommicron wave, from December 4, 2021 to January 15, 2022.
Prior to omicron, only 14 cases of COVID-19-related croup appeared from March 2020 to early December 2021, usually with no more than one case per week. Of those cases, 12 went to the emergency department and two were hospitalized. But at the peak of Massachusetts’s ommicron rise in early 2022, the COVID-19-associated croup spiked with about two dozen cases in one week. Of the 61 cases of croup during the ommicron period, 54 went to the emergency department and seven were hospitalized.
No other COVID-19 spike was linked to a spike in croup cases. And in the cases where doctors tested children for possible co-infections, all children tested negative, except for one who tested positive for rhinovirus (the common cold).
The researchers also noted that cases of COVID-19-associated croup, seen largely in the omicron period, seemed to skew toward more severe croup than what is seen in cases caused by other viral infections. The COVID-19-associated croup caused more hospitalizations and required more redoses of treatments than expected, the researchers report. Four cases required intensive care, but none resulted in invasive ventilation or death.
For non-COVID-19 related cases, croup is often considered mild and can sometimes be treated at home with simple treatments and over-the-counter medications, such as acetaminophen (Tylenol). Most importantly, experts recommend taking a baby or toddler with croup into damp or cold air — a steamy bathroom or outside on a winter’s night (croup is often worst at night). The cold and moisture help relieve inflammation and loosen mucus. But in cases where a young child is having trouble breathing, a trip to the emergency department can provide quick relief with a steroid, such as the glucocorticoid dexamethasone, to reduce inflammation.
While the Massachusetts study is limited by its small size and single location, the authors claim it provides compelling preliminary evidence that omicron infections cause croup, sometimes severe croup, and the study warrants further investigation.
“Two years after the COVID-19 pandemic, the pathogenicity, infectivity and manifestations of new variants of SARS-CoV-2 are dynamic and unique,” they write. “Kroep can represent another such new presentation.”
