Increased bronchiolitis burden and severity after the pandemic: a national multicentric study.

Background: The coronavirus 2019 (COVID-19) related containment measures led to the disruption of all virus distribution. Bronchiolitis-related hospitalizations shrank during 2020–2021, rebounding to pre-pandemic numbers the following year. This study aims to describe the trend in bronchiolitis-related hospitalization this year, focusing on severity and viral epidemiology. Methods: We conducted a retrospective investigation collecting clinical records data from all infants hospitalized for bronchiolitis during winter (1st September-31th March) from September 2018 to March 2023 in six Italian hospitals. No trial registration was necessary according to authorization no.9/2014 of the Italian law. Results: Nine hundred fifty-three infants were hospitalized for bronchiolitis this last winter, 563 in 2021–2022, 34 in 2020–2021, 395 in 2019–2020 and 483 in 2018–2019. The mean length of stay was significantly longer this year compared to all previous years (mean 7.2 ± 6 days in 2022–2023), compared to 5.7 ± 4 in 2021–2022, 5.3 ± 4 in 2020–2021, 6.4 ± 5 in 2019–2020 and 5.5 ± 4 in 2018–2019 (p < 0.001), respectively. More patients required mechanical ventilation this winter 38 (4%), compared to 6 (1%) in 2021–2022, 0 in 2020–2021, 11 (2%) in 2019–2020 and 6 (1%) in 2018–2019 (p < 0.05), respectively. High-flow nasal cannula and non-invasive respiratory supports were statistically more common last winter (p = 0.001 or less). RSV prevalence and distribution did not differ this winter, but coinfections were more prevalent 307 (42%), 138 (31%) in 2021–2022, 1 (33%) in 2020–2021, 68 (23%) in 2019–2020, 61 (28%) in 2018–2019 (p = 0.001). Conclusions: This study shows a growth of nearly 70% in hospitalisations for bronchiolitis, and an increase in invasive respiratory support and coinfections, suggesting a more severe disease course this winter compared to the last five years. [ABSTRACT FROM AUTHOR]