Severe acute respiratory infections during the influenza A(H1N1)2009 pandemic in Belgium: first experience of hospital-based flu surveillance

In September 2009, as part of the surveillance during the Influenza A(2009) pandemic, Bel-gium introduced a web-based surveillance system aimed at recording hospitalisations and deaths attributable to Influenza in real time. We present the web-based application developed for the pandemic as well as a descriptive analysis of Severe Acute Respiratory Infection (SARI) cases reported through this system. From 1 September to 31 December 2009, 1723 SARI-related hospitalisations potentially due to influenza were reported in Belgium. The median age of the patients was 29 years (range: < 1 year-99 years). Among SARI-hospitalised patients 68% were aged less than 45 years, 10.6% were vaccinated with the seasonal influenza vaccine and 7.5% with the pandemic influenza vaccine. No deaths were recorded. This first experience showed the feasibility of getting real-time information from hospitals during a public health crisis. However, the absence of death detected through the system highlighted the importance of better defining the severity of the hospital cases.