The Omicron coronavirus variant has caused a spike in cases of the potentially severe respiratory condition in infants and young children, according to a hospital study recently published in the Journal of Pediatrics.
The study is small, focusing only on cases associated with COVID-19 at a large children’s hospital in Massachusetts during the pandemic. But it does provide some preliminary data on the topic and support anecdotes from health care providers that the latest variant of the epidemic is causing more cases of laryngitis and bronchitis – aka diphtheria – in younger children than previous variants.
In general, croup is a common condition of the upper respiratory tract in which significant inflammation and swelling of the larynx and trachea develop, compromising breathing. Some viral infections usually cause swelling, but allergies and other irritants can be the cause. Croup can occur at any age but most commonly affects the upper airways of infants and young children, ages 3 months to 5 years.
Croup got its name from the “choking” cough it causes, which is sometimes described as a seal-like barking cough. Other distinguishing features of the condition are the harsh, unpleasant sound when the patient breathes – stridor inhales – and shortness of breath.
Before the omicron wave, COVID-19 was associated with diphtheria in some children, but it does not appear to be a common consequence of pandemic infection. That changed during the Omicron wave when health care providers reported seeing more cases of diphtheria associated with COVID-19 in young patients.
While data is still sparse about why this occurs, experts speculate that early variants and predecessors of SARS-CoV-2 tend to target the lower respiratory tract, leading to more serious disease in older age groups. Meanwhile, Omicron appears to tend to be upper respiratory, which may partly explain why it is transmissible and associated with relatively milder disease in the older age groups.
But in very young children — who have small airways and are still ineligible for COVID-19 vaccinations — omicron appears to pose a new risk.
In the new study, researchers led by pediatrician Ryan Brewster at Boston Children’s Hospital surveyed hospital records for cases of croup associated with COVID-19 from March 2020 to January 15, 2022. They found only 75 cases — but 61 cases (81 percent) during the frame. The timeline of approximately one and a half months for the Omicron wave, from December 4, 2021, to January 15, 2022.
Before Omicron, only 14 cases of diphtheria associated with COVID-19 appeared from March 2020 to the beginning of December 2021, usually with no more than one case per week. Of these, 12 were taken to the emergency department, and two were hospitalized. But at the height of the Omicron rush in Massachusetts at the beginning of 2022, diphtheria associated with COVID-19 peaked at about two dozen cases in one week. Of the 61 cases of oomicron angina, 54 went to the emergency department, and seven were hospitalized.
No other peak of COVID-19 has been linked to a rise in diphtheria cases. And in cases where doctors tested children for possible co-infections, all children tested negative, except for those who tested positive for rhinovirus (the common cold).
The researchers also noted that cases of diphtheria associated with COVID-19, which were most frequently seen in the oomicron period, appeared to deviate into more severe diphtheria than seen in cases caused by other viral infections. The researchers reported that the COVID-19-related group caused more hospitalizations and required repeat doses of more treatments than expected. Four cases required intensive care, although none resulted in invasive ventilation or death.
For cases not associated with COVID-19, croup is often considered mild and can sometimes be managed at home with simple treatments and over-the-counter medications, such as acetaminophen (Tylenol). Most importantly, experts recommend bringing an infant or young child with croup to moist or cool air – a steamy bath or outside on a winter’s night (croup is often worse at night). Coolness and moisture help reduce inflammation and loosen mucus. But in cases where a young child has trouble breathing, a trip to the emergency department can provide quick relief with a steroid, such as the glucocorticoid dexamethasone, to reduce inflammation.
Although the Massachusetts study is limited by its small size and individual location, the authors argue that it provides compelling preliminary evidence that oomicron infection causes diphtheria, and sometimes severe diphtheria, and the study warrants further investigation.
“Two years after the COVID-19 pandemic, the pathogenicity, infection, and manifestations of novel SARS-CoV-2 variants are dynamic and unique,” they wrote. Croup might be another such new show.