[Surveillance of influenza in France (author's transl)].

The collection of data for influenza surveillance is difficult because clinical cases cannot easily be notified by practitioners and because only a few cases are studied by specific biological methods. In different countries, several indices are used such as: morbidity returns, mortality returns, absenteeism returns preferably in combination. In France, the two National Reference Centres in Paris and Lyon coordinate the activities of all diagnostic laboratories where influenza is detected by collecting and redistributing their findings and by identifying the strains they isolate. Furthermore, a collaborative network of physicians and institutions is being organised to provide a complete coverage of the country. I.N.S.E.R.M. and the National Centres have set up during the last two winters a new method of specific surveillance in school children: it combines observation of absenteeism peak in randomly selected classes and etiologic diagnosis by virus isolation. Surveillance of such a group, particularly sensitive to epidemic spread and probably partly responsible for it, was very efficient: early isolations were obtained and the presence of epidemics was detected before overt outbreaks occurred.