IFNG and COVID-19: Persistently elevated fIL-18 in severe COVID-19 may underlie the finding that elevated IFN-gamma after day 10 of symptoms is independently associated with death [42]; IFN-gamma potently activates macrophages [43] and macrophage-mediated destruction of lung architecture via infiltration of extra pulmonary tissue is a hallmark of fatal COVID-19 [44].