Bronchiolitis Hospitalization Surge and Increased Severity Post-Pandemic: Italian Multicenter Study

The SARS-CoV-2 pandemic led to strict measures in Italy, reducing overall virus spread and nearly eliminating bronchiolitis in the winter of 2020. Subsequently, bronchiolitis patterns shifted, with increased cases in summer and an early winter peak. Limited data exist on bronchiolitis in the winter of 2022. We studied clinical records of infants (0-12 months) hospitalized for bronchiolitis during winter (September 1 to March 31) from 2018 to 2023 at six Italian hospitals. Over the five winter seasons considered, we identified a total of 2,428 infants hospitalized for bronchiolitis: 953 during the 2022 winter, 563 in the 2021 winter, 34 in the 2020 winter, 395 in the 2019 winter, and 483 in the 2018 winter. In the 2023 winter, the length of stay was longer (mean 7.2 ± 6 days), compared to 5.7 ± 4 in the 2021 winter, 5.3 ± 4 in the 2020 winter, 6.4 ± 5 in the 2019 winter, and 5.5 ± 4 in the 2018 winter (p<0.001). 38 patients required intubation in the 2022 winter (4%), compared to 6 (1%) the previous winter, 0 during the 2020 winter, 11 (2%) in the 2019 winter, and 6 (1%) in the 2018 winter; this difference is statistically significant (p<0.05). During the 2022 winter, respiratory supports, including high-flow nasal cannula, continuous positive airway pressure, and non-invasive ventilation, were used more frequently (p=0.001 or less). We observed a higher prevalence of coinfections among patients requiring invasive ventilation or access to intensive care units. We identified an unprecedented number of infants hospitalized for bronchiolitis in the 2022 winter. This period saw a more severe course, with longer stays, increased respiratory support, and more ICU admissions compared to the previous four years.