Very high intensity of the bronchiolitis epidemic during the 2022-2023 season in France

BACKGROUND: During epidemic seasons, bronchiolitis affects young children with a large burden in emergency departments (EDs). Following the beginning of the COVID-19 pandemic and 2 perturbed seasons, the aim of this study was to assess the burden of bronchiolitis in EDs in terms of visits and post-discharge hospitalisations in 2022-23 compared with the pre-COVID seasons. METHODS: Santé publique France, collects ED data through OSCOUR® (95% of French ED visits). ED visits with a medical diagnosis of bronchiolitis (based on ICD-10 codes) in children under 2 years of age (yo) were included. The burden of the 2022-23 epidemic season (from 2022-W36 to 2023-W16) was compared with that of the pre-COVID seasons (2015-16 to 2019-20), by age group, in terms of visits and hospitalisations after discharge, in particular in intensive care units (ICUs) (annual data and means). RESULTS: In 2022-23, 99,864 ED visits for bronchiolitis and 31,505 post-discharge hospitalisations were registered for children under 2 yo (vs. respectively +49% and +44% compared to the pre-COVID seasons). It represented 15% of all ED visits and 33% of all hospitalisations after discharge of this age group (vs. 10% and 23% pre-COVID). Among children under 1 year, distribution of bronchiolitis ED visits by age group remained relatively stable in comparison with pre-COVID seasons. For children under 6 months, bronchiolitis accounted for 27% of all ED visits (19% pre-COVID), 45% of all hospitalisations (35% pre-COVID) and more than 70% of hospitalisations referred in ICU during 7 weeks (2 weeks pre-COVID). CONCLUSIONS: The 2022-2023 bronchiolitis epidemic was of extreme intensity in France with a highest impact than for pre-covid seasons and leading to saturation of EDs. These findings were consistent with an increase in respiratory illness in children during the 2022-23 winter season, and raised questions about the impact of the COVID-19 pandemic on their epidemiology and a potential decrease of immunity. KEY MESSAGES: • Beside a very high intensity for the 2022-23 bronchiolitis epidemic, distribution of ED visits by age group remained relatively stable among children under 1 year. • In 2022-2023, among children under 6 months, during nearly two months (7 weeks), more than 70% of hospitalizations after discharged referred in ICU were due to bronchiolitis.