Community-based influenza surveillance has been conducted in France for many years by the Sentinelles and GROG networks. The National Reference Centers for Influenza Viruses are responsible for identifying influenza strains, which are primarily submitted by physicians in the GROG network and by a network of hospital virology laboratories. In light of the risk of an influenza pandemic, the InVS has strengthened weekly influenza surveillance by implementing two new systems (reactive surveillance of influenza-related mortality and surveillance of severe pediatric cases), whose objectives are to identify any abnormal changes in influenza epidemiology as quickly as possible, adapt control measures, and monitor their impact. Surveillance of influenza-related mortality is carried out by 22 regional health departments (Ddass), which report to the InVS the number of “all-cause” death certificates and influenza-related deaths, as well as the corresponding individual data for the latter. The surveillance network for severe pediatric cases relies on the services of the Francophone Group for Pediatric Intensive Care and Emergency Medicine to report weekly to the InVS the number of severe pneumonia cases admitted to their units. Furthermore, the InVS has established a syndromic surveillance system based on automated data collection from 34 emergency departments (22 located in the Île-de-France region). We conducted a retrospective analysis of emergency department visits related to influenza to determine whether this system could be integrated into the surveillance required to combat an influenza pandemic. During seasonal epidemics, influenza frequently causes clusters of acute lower respiratory tract infections (ALRIs) in elderly care facilities. The goal of strengthening surveillance of these clusters is to reduce mortality and morbidity in these settings. Reports from DDASS, CCLIN, or CIRE. Early identification of clusters of ARI, implementation of control measures, assessment of their impact, and investigation of the most severe or uncontrolled outbreaks are the key elements of this surveillance. During the 2004–2005 season, the influenza epidemic in France developed between week 3/2005 and week 12/2005. The A(H3N2) virus was largely responsible for the epidemic wave, which peaked in week 6 (the week of February 7, 2005). The epidemic was classified as moderate. 228 influenza-related deaths were reported and 219 were described. The highest number of deaths (40 deaths) was reported one week after the peak of the epidemic. 95% of patients were over 64 years of age; only one patient was under 5 years of age. Analysis of the 67 admissions reported by the weekly surveillance system for pediatric hypoxemic pneumonia shows an increase in admissions during the two weeks preceding the peak of the influenza epidemic. Of the 52 cases described, only one patient had a confirmed influenza infection. Six deaths were reported, including 5 among children with risk factors. The emergency department surveillance system reported 1,765 visits with a primary diagnosis of influenza in the Île-de-France region and 620 outside the Île-de-France region. In the Île-de-France region, the peak in emergency department visits for influenza coincided with the peak of the epidemic reported by community-based influenza surveillance systems. In hospitals participating in the surveillance network, approximately 3% of patients with a primary diagnosis of influenza were hospitalized following their visit to the emergency department in the Île-de-France region, and 8% in hospitals located outside the Île-de-France region. The patients most frequently hospitalized were young children and the elderly. Weekly analysis of this surveillance will be operational for the 2005–2006 flu season. The influenza virus was isolated in 46 of the 71 clustered cases of acute lower respiratory infections reported in elderly care facilities during the season. The number of reports increased significantly compared to the previous season (15 cases), which primarily reflects greater awareness among care facilities. Infection control measures were often implemented. However, the initiation of prophylactic treatment was delayed, with prescriptions, for reported cases, occurring on average 13 days after the onset of symptoms. (R.A.)