ISG15 and COVID-19: By intersecting the resulting DEGs from these three analyses, we further scrutinized the common DEGs, leading to the identification of 10 hub genes: IFI44L, IFI44, RSAD2, ISG15, IFIT3, OAS1, EIF2AK2, IFI27, OASL, and EPSTI1. These genes were significantly up-regulated in COVID-19, exerting roles in immune regulation.