Study Shows That Croup Is A Common Manifestation In Children Infected With The Omicron Variants

Pediatric COVID-19: A new study conducted by researchers from the Division of Emergency Medicine, Children's Healthcare of Atlanta at Scottish Rite, Atlanta-USA has found that most pediatric patients develop croup upon being infected with the SARS-CoV-2 Omicron variants.


 
Croup is an infection of the upper airway, which obstructs breathing and causes a characteristic barking cough. The cough and other signs and symptoms of croup are the result of swelling around the voice box (larynx), windpipe (trachea) and bronchial tubes (bronchi).
 
The Pediatric COVID-19 study team in a retrospective analysis described weekly croup and corresponding viral prevalence patterns in a pediatric quaternary care system in metropolitan Atlanta. The study team characterize a series of 24 patients with croup associated with SARS-CoV-2 infection and show that this clinical presentation increased substantially in frequency during the period of high Omicron vs Delta transmission.
 
Typically, croup represents inflammation of the subglottic upper airway mucosa in children associated with respiratory distress due to epithelial-level edema and airflow obstruction. The majority of croup presentations to the emergency department (ED) are attributable to acute viral infection. Similar to other viral-associated respiratory illnesses, such as bronchiolitis and asthma exacerbations, croup presentations tend to fluctuate in frequency, depending on the local prevalence of specific viral pathogens. Approximately 75% of cases of croup are caused by 1 of 4 parainfluenza virus (PIV) subtypes, with the remaining 25% caused by common seasonal respiratory “cold” viruses that are included in standard multiplex respiratory viral panel (RVP) testing, including endemic coronaviruses.
 
The study findings were published in the peer reviewed Journal of Pediatric Infectious Diseases Society.
https://academic.oup.com/jpids/advance-article/doi/10.1093/jpids/piac032/6581272?login=false

Croup which is but  inflammation of the subglottic upper airway mucosa manifest as respiratory distress airflow obstruction in children. In addition, it is associated with epithelial-level edema, and most emergency department (ED) admissions occur due to an acute viral infection.
 
The reported frequency of the presentations seems to be variable based on the local prevalence and specific viral pathogens. About 75% of the cases result from a particular parainfluenza virus (PIV), among its four subtypes, while the remaining occur due to common seasonal respiratory viruses. These common cold viruses, as well as the endemic coronaviruses, are included in the standard multiplex RVP (respiratory viral panel testing).
 
Only a negligible number of cases (<10) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-associated croup had been reported before the surge in Omicron variant-related cases. For these, multiplex RVP testing confirmed SARS-CoV-2 etiology.
 
However, from December 2021 to January 2022, metropolitan Atlanta saw a sudden rise in the prevalence of coronavirus disease 2019 (COVID-19) cases, which was evident through an abrupt escalation in the ED cases of croup .
 
The study team aimed to characterize the clinical features of SARS-CoV-2-associated croup among children presenting to the ED during the phase when Omicron variant transmission was high.
 
Acute SARS-CoV-2 infection-related ED visits were identified, and the frequency of croup was compared among these pediatric patients during the study period and in the prior Delta phase.
 
For the study, the patterns of ED visits were analyzed during both time periods to determine whether the presentations could be attributed to SARS-CoV-2 strains. Cases were categorized into period 1 – Omicron-dominant (between December 2021 to January 2022) and period 2 – Delta-dominant (between July 2021 to August 2022).
 
The study team next identified cases with concurrent croup diagnosis and the frequency of this co-association was compared between the two time periods. The impact on younger children during the two outbreaks was characterized by comparing the significance of the proportional differences.
 
In all, 218,387 ED visits were recorded from 2021 to 2022; of these, 15.9% were inpatient admissions.
 
Importantly, the Omicron surge saw a tripling of ED croup visits which concurred with the rise in SARS-CoV-2 prevalence. The admission rate during this phase was 12.1% to 15.6%. While the overall admission rate for croup during this period ranged from 12.1% to 15.6%.
 
It was also found that all other respiratory viral infections occurred less frequently during the Omicron period. However, during the Delta period, respiratory syncytial virus (RSV) and rhinovirus/enterovirus (RV/EV) caused unexpectedly numerous hospitalizations.
 
During the Delta wave, 44,940 ED visits were recorded; among these, 4.7% could be attributed to COVID-19. Of the COVID-19 cases, 28.8% were pediatric patients (0-4 years of age); among these, 17.6% were hospitalized. Of all the COVID-19 cases during this Delta period, 0.9% were diagnosed with croup.
 
During the Omicron period a total of 15,423 ED visits occurred, of which 12% were related to COVID-19. Among patients with COVID-19, 51.2% were children (0-4-year-olds) – this translated into a 77.8% hike in the proportion (of COVID-19 cases in this age group) when compared to the Delta period. Among these children with COVID-19, 16.1% were hospitalized; 10.8% were diagnosed with croup––which accounted for a 12-fold rise in COVID-19-associated croup.
 
In all, 36 patients with croup underwent multiplex RVP testing; 66.7% were SARS-CoV-2-positive. Among the SARS-CoV-2-positive patients, 24 were of a median age of 12 months – 18 were males, and six were females. While 10 were Caucasians, seven were African American, five 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 hospital length of stay (LOS) was 24 hours and patients were managed according to the standard treatment protocol for croup.
 
Upon comparison to the SARS-CoV-2 Delta variant, the Omicron variant has greater transmissibility. It was observed that SARS-CoV-2 presentation-associated croup substantially increased in frequency during the Omicron phase of the COVID-19 pandemic.
 
In addition, COVID-19 diagnosis nearly doubled among children between 0-4 years old during the Omicron period compared to the Delta period.
 
The importance of proper measures among this susceptible population should be paid attention to.
 
It should be noted that upper respiratory tissue tropism was demonstrated by the Omicron variant. This aids the virus in adapting to new tissue to improve its fitness to enable better survival and higher transmissibility. Sweden recently reported numerous odynophagia and laryngitis cases among young adults during an Omicron dominant period, signifying the evolving tissue tropism of the pathogen.
 
The study findings supported a SARS-CoV-2-associated croup infectious syndrome that simulates croup due to other respiratory viruses, which escalated in frequency during the Omicron dominance. In addition, a dramatically increased incidence of croup was recorded in younger children with COVID-19 during the Omicron period than in the prior Delta period. Thus, ongoing efforts were validated to prevent COVID-19 from spreading to younger children, due to the negative effects of COVID-19 in this population.
 
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