The 1918–19 pandemic occurred in three waves: a mild first wave in spring and summer 1918, an extremely lethal second wave in autumn 1918, followed by a less severe third wave in winter 1919. Furthermore, the pattern of successive waves of varying severity also occurred in the 1957 and 1968 pandemic. It is not clear, however, whether past pandemics are an appropriate register for evaluating the current influenza pandemic evolution. In addition, no study has specifically analysed influenza A (H1N1) 2009 pneumonia during the 2010–11 influenza season.