Healthcare facilities (HFs) provide a conducive environment for the emergence and transmission of pathogenic infectious agents. Since 2001, the external reporting of certain rare or severe nosocomial infections (NIs) has been mandatory in French HFs in order to facilitate earlier detection, investigation, and control. For three emerging infections (glycopeptide-resistant Enterococcus, Clostridium difficile 027, and carbapenemase-producing Enterobacteriaceae), data from this detection and alert response system were mapped to the timeline of milestones marking these outbreaks and compared with available surveillance data to analyze commonalities. The reporting of NI allowed for the detection of these outbreaks, the early dissemination of control recommendations, support for HCFs in implementing these measures, and the evaluation of their impact. Two of these three outbreaks are currently under control. Complemented by appropriate microbiological expertise, the reporting system has proven its usefulness at every stage of outbreak management: proactive surveillance, detection, alert, and follow-up. The limitations of the system and the data it generates are discussed to propose improvement measures (enhanced support and training for healthcare facilities, the e-SIN remote reporting tool). (R.A.)