ISG15 and COVID-19: Many known signature-genes identified for COVID-19 (IFI27, OLFM4), RSV-LRTI (SIGLEC1, ISG15, IFI44) and PTB (MMP8, MMP9, DEFA1, DEFA1B, DEFA3 and DEFA4) are known to be associated with progressive severity87, showing the reproducibility of our findings.