To select variables that predict severe influenza, patient characteristics (influenza type, age, duration of illness, sex, ethnicity, and bacterial status), and DEGs (MPO, PRTN3, ELANE, AZU1, BPI, CEACAM6, DEFA4, LCN2, CEACAM8, CTSG, RETN, OLFM4, RNASE3, DEFA3, MMP8, HP, DEFA1B, and LTF) were included in the LASSO regression analysis. Here, DEFA3 is linked to influenza.