Background <p>In France, early detection of bronchiolitis epidemics relies on a multi-source surveillance system. However, this system is unable to measure epidemic severity in real time. Such information would enable faster alerts to decision-makers and medical facilities, allowing healthcare provision to be adapted more effectively. This additional information would provide healthcare decision-makers and care structures to be alerted more quickly and to adapt their healthcare provision in a reactive way. In this context, we conducted a study to assess the severity of bronchiolitis epidemics in children under two years of age, from 2017/18 to 2022/23, in Nouvelle-Aquitaine, France.</p> Methods <p>The Moving Epidemic Method (MEM) was used to assess the severity of bronchiolitis epidemics, based on three indicators, obtained from three data sources: (1) virus transmissibility, using data from the SOS Medecins network; (2) impact on the hospital system, assessed via emergency departments (ED) data and (3) gravity, using hospital data. Epidemic thresholds and intensity levels were determined by estimating the parameters of MEM.</p> Results <p>The 2020/21 epidemic was delayed and less severe compared to preceding seasons (2017–2020) across all indicators. In contrast, the 2021/22 and 2022/23 epidemics began early, with prolonged durations. Notably, the 2022/23 epidemic was particularly severe in terms of its impact on the hospital system.</p> Conclusions <p>The intensity of bronchiolitis epidemics in Nouvelle-Aquitaine (2017–2023) was assessed using MEM. This method is a simple, rapid and effective tool for guiding public health interventions.</p>