The ten common DEGs (PCOLCE2, HLA_DPA1, LOC653061, TDRD9, MPO, HLA_DQA1, MAOA, S100P, RAP1GAP, and CA1) that were obtained by overlapping genes from computing the three algorithms [LASSO regression (Fig. 4a, b), SVM-RFE algorithms (Fig. 4c, d), and RF (Fig. 4e, f) are candidate key genes for severe influenza (Fig. 4g). The gene discussed is TDRD9; the disease is influenza.