Moreover, the baseline differences of greater age and the higher number of co-morbid illnesses between the two study periods may be also a possible explanation for the higher morbidity and mortality documented during the post-pandemic influenza season. In this respect, studies involving patients with pandemic (H1N1) 2009 found that older patients had the highest case fatality rate. Additionally, sev-eral comorbidities have been associated with complications, ICU admission and mortality during pandemics [2–6].