Bronchiolitis 2022–2023: One of the most unexpected outbreaks over this past decade, Nouvelle-Aquitaine, France

• The 2022–23 outbreak of bronchiolitis was characterized by an early onset of an exceptional size with a significantly greater intensity than that observed in previous outbreaks. • A pronounced impact on the healthcare system was observed. • An epidemiological monitoring system facilitated description of the scale and impact of the outbreak, and transmitted information to health authorities that contributed to anticipation of the healthcare demand that would ensue. Since the Covid-19 pandemic, bronchiolitis outbreaks have been subject to disrupted seasonality, and a major impact on the healthcare system was observed in 2022–23. The aim of this article is to describe the characteristics of the 2022–23 bronchiolitis epidemic in the Nouvelle-Aquitaine region, and its impact on the healthcare system. We described the indicators of dynamics, intensity, severity and impact provided by the bronchiolitis monitoring in place, and compared these with those from previous seasons. The intensity of the 2022–23 epidemic (emergency department visits: 23 %; SOS Médecins acts: 15 %), and its impact in terms of bronchiolitis-related hospitalizations (45 %) were higher than in previous seasons (p < 0.05). In addition to earliness, the 2022–23 bronchiolitis epidemic was significant as regards its exceptional scale and major impact on the hospital system, requiring adaptation of the preexisting healthcare offer in response to the anticipated demand.