It has been previously reported for SARS-CoV and influenza infections that dysregulation of the urokinase pathway including U-PA(PLAU) and its inhibitor PAI-1(SERPINE1) might contribute to the severity of lung disease by altering the dynamics of fibrin breakdown and intra-alveolar fibrin levels and subsequently inflammation [21], [22]. This evidence concerns the gene SERPINE1 and influenza.