Evidence of croup associated with SARS-CoV-2

Croup, an inflammation of the lining of the subglottic upper airways, manifests as airflow obstruction in respiratory distress in children. In addition, it is associated with edema in the epithelium, and most emergency room admissions are due to acute viral infection.

Étude : Croup Associated With SARS-CoV-2 : Pediatric Laryngotracheitis During the Omicron Surge. Crédit image : rumruay / Shutterstock

The frequency of presentations appears to be variable depending on local prevalence and specific viral pathogens. About 75% of cases are due to a particular parainfluenza virus (PIV), among its four subtypes, while the rest are due to common seasonal respiratory viruses. These common cold viruses, as well as endemic coronaviruses, are included in the standard multiplex RVP (respiratory viral panel testing).

A negligible number of cases (

From December 2021 to January 2022, metro Atlanta experienced a sudden increase in the prevalence of coronavirus disease 2019 (COVID-19) cases, which was manifested by a sharp escalation in emergency room croup cases.

The study

A new study published in the Journal of Pediatric Infectious Diseases Society (en anglais) aimed to characterize the clinical features of SARS-CoV-2-associated croup in children presenting to the emergency department during the phase when transmission of the Omicron variant was high.

Emergency room visits related to acute SARS-CoV-2 infection were identified and the frequency of croup was compared in these pediatric patients during the study period and during the prior Delta phase.

Trends in emergency department visits were analyzed over both time periods to determine if presentations could be attributed to strains of SARS-CoV-2. The cases were classified into two categories: Period 1 – Omicron dominant (between December 2021 and January 2022) and Period 2 – Delta dominant (between July 2021 and August 2022).

Subsequently, cases with a co-diagnosis of croup were identified, and the frequency of this co-association was compared between the two periods. The impact on younger children during the two epidemics was characterized by comparing the significance of the proportional differences.


Overall, 218,387 emergency room visits were recorded between 2021 and 2022; 15.9% of them resulted in hospitalizations. During the Omicron period, the number of ER visits for croup tripled, matching the increase in the prevalence of SARS-CoV-2. The admission rate during this phase increased from 12.1% to 15.6%. The overall admission rate for croup during this period ranged from 12.1% to 15.6%.

Interestingly, all other viral respiratory infections occurred less frequently during the Omicron period. However, during the Delta period, respiratory syncytial virus (RSV) and rhinovirus/enterovirus (RV/EV) caused an unexpected number of hospitalizations.

During the Delta period, 44,940 emergency room visits were recorded; of these, 4.7% could be attributed to COVID-19. Of the COVID-19 cases, 28.8% were pediatric patients (0-4 years); among them, 17.6% were hospitalized. Of all COVID-19 cases recorded during the Delta reporting period, 0.9% were diagnosed as croup cases.

A total of 15,423 ER visits occurred during the Omicron period, 12% of which were related to COVID-19. Of the patients with COVID-19, 51.2% were children (0-4 years old) – translating to a 77.8% increase in the proportion (of COVID-19 cases in this group of age) relative to the Delta period. Of these children with COVID-19, 16.1% were hospitalized; 10.8% were diagnosed with croup – representing a 12-fold increase in croup associated with COVID-19.

Overall, 36 patients with croup underwent multiplex PVR testing; 66.7% were positive for SARS-CoV-2. Of the SARS-CoV-2 seropositive patients, 24 had a median age of 12 months, 18 were male and six were female. Ten were Caucasian, seven were African American, five were Hispanic, and two were Asian.

Of these 24 pediatric patients, 11 were hospitalized – two in the intensive care unit (ICU) and one requiring supplemental oxygen with heliox. The median length of hospital stay was 24 hours and patients were managed according to standard croup treatment protocol.


Compared to the Delta variant of SARS-CoV-2, the Omicron variant has greater transmissibility. The frequency of croup associated with SARS-CoV-2 presentation has been observed to increase significantly during the Omicron phase of the COVID-19 pandemic. In addition, the diagnosis of COVID-19 almost doubled among children aged 0-4 years during the Omicron period compared to the Delta period.

Therefore, the importance of vaccination efforts cannot be overlooked, especially within this susceptible population. In addition, upper respiratory tissue tropism has been demonstrated by the Omicron variant. This helps the virus adapt to new tissues to improve its survivability and transmissibility. Sweden recently reported numerous cases of odynophagia and laryngitis in young adults during a period of Omicron dominance, indicating the development of tissue tropism of the pathogen.

The results confirmed the existence of an infectious croup syndrome associated with SARS-CoV-2 that mimics croup due to other respiratory viruses, the frequency of which increased during Omicron dominance. In addition, young children with COVID-19 had a significantly higher incidence of croup during the Omicron period than during the earlier Delta period.

Thus, continued efforts have been validated to prevent the spread of COVID-19 to younger children, due to the negative effects of COVID-19 in this population.



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