Inclusion Criteria:  Adult SARI patients with 2019-ncov infection confirmed by PCR; Absolute value of lymphocytes < 0. 6x 109/L; Severe respiratory failure within 48 hours and requires admission to ICU. (severe respiratory failure was defined as PaO2/FiO2 < 200 mmHg and was supported by positive pressure mechanical ventilation (including non-invasive and invasive mechanical ventilation, PEEP>=5cmH2O))  Exclusion Criteria:  Age < 18 A history of renal failure (unless recovered for at least 6 months), lactic acidosis, recurrent or severe hypoglycemia. A history of known glucose-6-phosphate dehydrogenase (G6PD) deficiency. Other uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements Allergic to experimental drugs and patients have the following conditions: Medical records of cirrhosis Myocardial infarction, developed after the patient was included in the study, but before the intervention bleeding, developed after the patient was included in the study, but before the intervention connection to artificial lung ventilation developed after the patient was included in the study, but before the intervention Active infection, or chronic or persistent infection that might worsen with immunosuppressive treatment (e.g., HIV, hepatitis B virus, hepatitis C virus, tuberculosis [TB]) Liver disease Renal disease Pregnancy Lactation Depressive disorder Body mass index less than 18 points or higher than 25 points Contraindications for hormonal contraception or intrauterine device. Autoimmune diseases A history of organ, bone marrow or hematopoietic stem cell transplantation Patients receiving anti-hcv treatment The competent physician considered it inappropriate to participate in the study