Every year, from November 1 to April 15, Santé publique France monitors severe cases of influenza admitted to intensive care units in order to assess the severity of the epidemic, anticipate potential overcrowding in healthcare facilities, and adjust control measures as necessary.

All intensive care units and certain critical care units are asked to report, using a regional reporting form, any patient admitted to intensive care who presents with:

• - a biologically confirmed diagnosis of influenza.

• - OR a severe clinical presentation with no other identified cause, where the clinical presentation and medical history suggest a diagnosis of influenza even if biological confirmation cannot be obtained (probable case).

At the same time, virological surveillance is also being implemented using data from the virology laboratories at the University Hospitals of Toulouse, Nîmes, and Montpellier to monitor the circulation of the influenza virus.