* age ≤18 and ≥80 years old * onset of symptoms \>8 days (immunosuppressed patients are excluded from the time limit when they become chronic carriers of the virus) * corticosteroid administration at a dose of \>0.75mg/kg (methylprednisolone equivalent) * multiple organ failure * ards (acute respiratory distress syndrome) * mechanical ventilation * patients who received atg, or campath, or other t-cell-suppressing monoclonal antibody within 28 days prior to admission * patients with concomitant confirmed infection from another pathogen or with very high procalcitonin (pct) that may indicate additional infection * enrollment in another clinical trial * pregnancy * inability to sign informed consent form * judged ineligible by at the treating physician (treating physician's discretion) * bilirubin ≥2x of upper normal limit * ast ≥ 2x of upper normal limit * creatinine ≥ 2x of upper normal limit or with dialysis/hemodialysis needs * karnofsky score ≤50

* age ≤18 and ≥80 years old * onset of symptoms \>8 days (immunosuppressed patients are excluded from the time limit when they become chronic carriers of the virus) * corticosteroid administration at a dose of \>0.75mg/kg (methylprednisolone equivalent) * multiple organ failure * ards (acute respiratory distress syndrome) * mechanical ventilation * patients who received atg, or campath, or other t-cell-suppressing monoclonal antibody within 28 days prior to admission * patients with concomitant confirmed infection from another pathogen or with very high procalcitonin (pct) that may indicate additional infection * enrollment in another clinical trial * pregnancy * inability to sign informed consent form * judged ineligible by at the treating physician (treating physician's discretion) * bilirubin ≥2x of upper normal limit * ast ≥ 2x of upper normal limit * creatinine ≥ 2x of upper normal limit or with dialysis/hemodialysis needs * karnofsky score ≤50

age ≤18 and ≥80 years old onset of symptoms >8 days (immunosuppressed patients are excluded from the time limit when they become chronic carriers of the virus) corticosteroid administration at a dose of >0.75mg/kg (methylprednisolone equivalent) multiple organ failure ards (acute respiratory distress syndrome) mechanical ventilation patients who received atg, or campath, or other t-cell-suppressing monoclonal antibody within 28 days prior to admission patients with concomitant confirmed infection from another pathogen or with very high procalcitonin (pct) that may indicate additional infection enrollment in another clinical trial pregnancy inability to sign informed consent form judged ineligible by at the treating physician (treating physician's discretion) bilirubin ≥2x of upper normal limit ast ≥ 2x of upper normal limit creatinine ≥ 2x of upper normal limit or with dialysis/hemodialysis needs karnofsky score ≤50

age ≤18 and ≥80 years old onset of symptoms >8 days (immunosuppressed patients are excluded from the time limit when they become chronic carriers of the virus) corticosteroid administration at a dose of >0.75mg/kg (methylprednisolone equivalent) multiple organ failure ards (acute respiratory distress syndrome) mechanical ventilation patients who received atg, or campath, or other t-cell-suppressing monoclonal antibody within 28 days prior to admission patients with concomitant confirmed infection from another pathogen or with very high procalcitonin (pct) that may indicate additional infection enrollment in another clinical trial pregnancy inability to sign informed consent form judged ineligible by at the treating physician (treating physician's discretion) bilirubin ≥2x of upper normal limit ast ≥ 2x of upper normal limit creatinine ≥ 2x of upper normal limit or with dialysis/hemodialysis needs karnofsky score ≤50