Introduction: The objectives of this study were to characterize bronchiolitis outbreaks in the Nantes metropolitan area, to examine the complementarity of different data sources, and to refine the criteria for outbreak alerts. Method: A retrospective analysis was conducted from 2007 to 2012 using hospital stays of children under 2 years of age diagnosed with bronchiolitis (PMSI) at the Nantes University Hospital and respiratory syncytial virus (RSV) isolates from the virology laboratory. Individual data from the SurSaUD® system (SOS Médecins Nantes) and OSCOUR® (emergency department visits) were used as supplementary data for 2011–2012. Results: During the study period, 2,721 hospital stays at the Nantes University Hospital were recorded, 64% of which occurred during periods of RSV circulation. Compared to previous epidemics, the 2011–2012 epidemic was shorter and more rapid, leading to an early peak (early December) and a high number of hospitalizations during the peak (n=64). Modeling the weekly numbers of hospitalized bronchiolitis cases between 2007 and 2012 (PMSI) using periodic regression allowed for the establishment of an epidemic alert threshold. Due to the good agreement between the PMSI and OSCOUR®, this threshold was used prospectively for real-time surveillance. Discussion and Conclusion: This study highlights the value and complementary nature of SurSaUD® system data for real-time surveillance of bronchiolitis epidemics. The dynamics of these epidemics vary from one region to another, which justifies a local analysis of surveillance data. These analyses allow hospitals to adjust their alert levels and adapt the organization of care to the epidemiological situation. (R.A.)