Severity of Illness in Bronchiolitis Amid Unusual Seasonal Pattern During the COVID-19 Pandemic

Abstract

Objective: We aimed to characterize recent trends in bronchiolitis at US children's hospitals and to compare severity of illness in bronchiolitis in the most recent year to the previous seasonal epidemics.

Methods: This is a cross-sectional study of visits for bronchiolitis in infants <24 months old from October 2016 to September 2021 at 46 US children's hospitals participating in the Pediatric Health Information Systems database. Study years were defined by 12-month periods beginning in October to account for typical winter epidemics that crossover calendar years. We used logistic and Fourier Poisson regression models to examine trends in outcomes and compare seasonality, respectively.

Results: The study included 389 411 emergency visits for bronchiolitis. Median age of infants with bronchiolitis was higher in October 2020 to September 2021 compared to previous epidemics (8 and 6 months, respectively, P < .001) The odds of hospitalization, ICU admission, invasive mechanical ventilation, and noninvasive ventilation did not differ in October 2020 to September 2021 compared to previous epidemics from October 2016 to September 2020 (all P > .05 for unadjusted models and models adjusted for age). Seasonality varied significantly among these 2 periods (P < .001).

Conclusions: Although the seasonality of bronchiolitis differed in October 2020 to September 2021, severity of illness in infants with bronchiolitis was consistent with previous epidemics.