Enterobacter sakazakii is an opportunistic bacterium responsible for serious infections, particularly in premature or low-birth-weight newborns: necrotizing enterocolitis, sepsis, or meningitis. These very rare infections (about 50 cases reported worldwide) have a high case-fatality rate (approximately 20%). In early December 2004, the French Institute for Public Health Surveillance (InVS) received, one week apart, two reports from two different hospitals of severe nosocomial infections (NI) caused by Enterobacter sakazakii that occurred between October 25, 2004, and December 7, 2004, in premature or low-birth-weight newborns. The first report concerned a death from meningitis at a hospital in Allier, and the second a death from meningitis, bacteremia, and gastrointestinal colonization at a hospital in Val d'Oise. The close timing of these very rare infections in two distant hospitals suggested a common source with widespread distribution. A national investigation was launched to quickly identify and control the source. (Introduction)