IRF9 and viral infectious disease: Phosphorylated STAT1 and STAT2 along with IRF9 form the ISGF3 complex, and the ISGF3 complex is translocated into the nucleus to bind IFN-stimulated response elements (ISREs), which results in the induction of numerous IFN-stimulated genes (ISGs) that interfere with multiple stages of the virus life cycle and limit viral infection [15, 16].