In December 2011, the Nantes University Hospital (CHU) faced a crisis caused by the seasonal bronchiolitis outbreak. To learn from this event, the Pays de la Loire Regional Health Agency (ARS) and the Nantes University Hospital conducted a "lessons learned" (Retex) review. The Regional Unit of the French Institute for Public Health Surveillance (InVS) in the Pays de la Loire region (Cire) contributed to this Retex by analyzing the characteristics of this outbreak. A retrospective analysis was conducted from 2007 to 2012 based on hospital stays of children under 2 years of age diagnosed with bronchiolitis (Medical Information Systems Program (PMSI)) at the Nantes University Hospital and on respiratory syncytial virus (RSV) isolates from the virology laboratory. Individual data from the SurSaUD® system (Health Surveillance of Emergency Department Visits and Deaths) (SOS Médecins Nantes and Oscour® emergency department visits (Organization for Coordinated Emergency Surveillance)) were used as supplementary data for 2011–2012. Over the 2007–2012 period, 2,721 hospital stays at the Nantes University Hospital were recorded among children under 2 years of age, 64% of which occurred during periods of RSV circulation. The annual hospitalization rate for RSV bronchiolitis in Nantes was estimated at an average of 22 per 1,000 children under one year of age. Compared to previous epidemics, the 2011–2012 epidemic unfolded more rapidly, leading to an early peak (early December) and a high number of hospitalizations during the week of the peak (n=62). Modeling hospitalizations for bronchiolitis between 2007 and 2012 using periodic regression allowed for the establishment of an epidemic alert threshold. This study highlights the value and complementary nature of data from the SurSaUD® system for real-time surveillance of bronchiolitis epidemics. These analyses enable hospitals to adjust their alert levels and adapt the organization of care to the epidemiological situation.