STAT3 and viral infectious disease: During viral infection, the expression of SOCS3 could be induced by viral protein or RNA (25, 28, 31), such as HIV-1 regulatory protein Tat, HCV core protein, RSV protein NS1, or 5′ triphosphate RNA of IAV, and by host cytokines, such as TNFα, IL-6, or IFNγ (7, 32–34), through various activating transcription factors, including nuclear factor-kappa B (NFκB), STAT3, and STAT1 (7, 32, 33).