Respiratory Viral Detection in Children Pre- and Post-COVID-19
What You Need to Know: In children under 5 years old presenting with bronchiolitis, pneumonia, or croup, there is a high likelihood of identifying at least 1 viral pathogen.
Article summary
Investigators from multiple institutions conducted a retrospective study to assess the association between respiratory viruses and specific acute respiratory illnesses, including bronchiolitis, pneumonia, and croup in children <5 years old, and evaluate changes in the viruses associated with these ARI prior to, and following, the COVID pandemic. For the study, they reviewed data in the New Vaccine Surveillance Network (NSVN). As part of the NSVN, respiratory tract samples are collected for clinical care or for research purposes and assayed for multiple respiratory viruses in children with 1 or more symptoms of ARI at 7 medical centers in the US. The proportion of children with each of the ARI conditions of interest in whom a respiratory virus was detected was determined, and frequency of each virus detected in patients with bronchiolitis, pneumonia, and croup calculated. Chi-square tests were used to compare changes in proportions of different viruses associated with each of the ARI syndromes during the prepandemic (2017–2019) and post-pandemic (2021–2023) periods.
Data were analyzed on 19,447 children, including 14,340 diagnosed with bronchiolitis, 4,423 with pneumonia, 2,367 with croup, 1,541 with bronchiolitis and pneumonia, 107 with bronchiolitis and croup, and 42 with pneumonia and croup. The median age of participants with bronchiolitis, pneumonia and croup was 8 months, 23 months and 18 months, respectively. At least 1 respiratory virus was detected in 89% cases of bronchiolitis, 81% of those with pneumonia, and 82% of patients with croup. Respiratory syncytial virus (RSV) was the most commonly detected virus associated with bronchiolitis (41% of cases) and pneumonia (26%). The most commonly detected virus in patients with croup was parainfluenza virus (28%). Rhinoviruses/enteroviruses (RV/EV) were the second most commonly detected virus in cases of bronchiolitis (18.9%), pneumonia (18.0%), and croup (14.4%).
Investigators’ conclusion: A respiratory virus was detected in a high proportion of children <5 years old with bronchiolitis, pneumonia, and croup.
Commentary
The authors of the current study performed a multicenter study to characterize viral detection and clinical presentation in children under 5 years old who presented with bronchiolitis, pneumonia, or croup between 2017–2023. The study included more than 21,000 children and found that >80% had at least 1 respiratory virus detected, most commonly RSV, RV/EV, and PIV. Most viruses were detected in similar proportions pre- and post-covid emergence except for PIV, which was decreased in croup cases post-COVID-19 onset. This was hypothesized to be due to the proportional increased detection of SARS-CoV-2 in the same timeframe.
Marilynn Chan MD, FAAP, San Francisco, CA
Editorial Board Member, AAP Grand Rounds
Source article: Teoh Z, Toepfer AP, Rohlfs C, et al. Viral detection in children <5 years with bronchiolitis, pneumonia, and croup, new vaccine surveillance network, 2017–2023. Pediatric Infect Dis Soc. 2025;14(11):piaf096. Published online October 17, 2025. [Link]
