Influenza surveillance in Switzerland

The Swiss Sentinel Network (SSN) has monitored influenza activity in Switzerland since 1986. Between 2600 and 6600 cases of influenza-like-illness (ILI) are reported each influenza season by the 150-200 general practitioners, internists and paediatricians who voluntarily participate in the SSN. Based on these figures, there are an estimated 100 000 to 230 000 cases of ILI in Switzerland each year during the main influenza-season (10 week-peak-periods). Among patients over 60 years, 13% to 20% developed pneumonia and 1.3% to 2.7% had to be hospitalised. This represents an estimated 1800 hospitalisations caused by influenza for the country as a whole each year. Based on data from the Swiss Medical Statistic VESKA (H+) there are an estimated 1600 hospitalisations per year; confirming the estimation of the SSN. Collaboration with the Swiss National Center for Influenza allows identifications of circulating influenza-strains and the determination of eventual deviations from the vaccine strains. The SSN has been a valuable surveillance tool during the last ten years and has provided useful data on the extent and importance of influenza in Switzerland. It therefore makes an important contribution to the elaboration of targeted and appropriate prevention measures against influenza.