Weekly monitoring of influenza impact in Belgium (1993-1995).

The primary objectives of an influenza monitoring programme are early detection of an epidemic and the identification of the viruses responsible. The healthcare impact of the disease is often some time after the epidemic. In Belgium data on the consequences of influenza are recorded weekly, which provides an early estimate of the severity of the epidemic. Data collected during 3 influenza seasons (1993-95) showed that during the peak of the very moderate influenza A/H3N2 outbreak in 1993-94, general practitioner consultations for acute respiratory infections increased by 100%, work absenteeism by 56%, total sales of pharmaceuticals by pharmacists by 26% and overall mortality by 14%. From these data, we estimated that 498,400 working days were lost during the peak week in Belgium in 1993, and 848 excess deaths were observed during the whole of the 1993-94 epidemic. 12% of those who died were aged less than 60 years. Hospitalisation data must be included in the future in order to complete the information that is essential for formulating public health policies on influenza vaccination.