[Surveillance of infectious diseases: principles and organisation in France in 2005].

Surveillance is a continuous and systematic process of collection, analysis, and diffusion of health data to all those who contributed to the collection and all those who need this data in order to take action. Surveillance activities first target health problems for which effective prevention or control measures are available. Surveillance objectives include the following-up of trends and changes in disease characteristics, evaluation of public health actions, and early detection of infectious diseases threats and epidemic and their investigation. The data produced by surveillance systems allow prioritizing public health actions and defining the objectives of infectious diseases control or prevention. The surveillance of infectious diseases relies on a large number of partners grouped in a public health network in which clinicians and microbiologists have a prominent role. In France, the surveillance of infectious diseases is based on mandatory notification of some diseases, national reference centers, networks of voluntary health professionals or services, and repeated surveys. The national surveillance is coordinated by a public health institute, "l'Institut de Veille Sanitaire", the missions of which are public health surveillance of the population, alerting health authorities in case of health threats, and identifying the determinants of changes in the population's health status.