STAT1 gain-of-function (GOF) mutations are described in patients with early-onset chronic mucocutaneus candidiasis, bacterial respiratory tract infections, and humoral immunodeficiency, while loss-of-function mutations are to be considered in patients with early-onset mycobacterial disease, osteomyelitis, respiratory tract infections, and Herpesviridae infection. Here, STAT1 is linked to Herpesviridae infectious disease.