Influenza season 2012–2013 in Europe: moderate intensity, mixed (sub)types

This paper summarizes influenza activity in the European Union/European Economic Area (EU/EEA) in 2012–2013. The influenza season 2012–2013 in Europe lasted from early December to late April. Overall the severity of the season could be described as moderate, based on the ILI/ARI consultation rates and the percentage of sentinel specimens positive for influenza compared to previous seasons. Both influenza A and B viruses circulating accounted for 47% and 53% of positive sentinel specimens, respectively, with both A(H1) and A(H3) varying for dominance. Compared to outpatients, the proportion of laboratory-confirmed influenza hospitalized cases infected by A(H1N1)pdm09 was significantly higher in middle-aged patients (33% vs. 17%, χ(2) = 66·6, P < 0·01). Despite a relatively good match between vaccine and circulating strains, vaccine effectiveness was estimated to be moderate.