inclusion criteria: 1.meet the definition of severe pneumonia(comply with any of the followings): shortness of breath,rr≥30 bpm; in a resting state:spo2≤93%; pao2/fio2≤300mmhg. 2.2019-ncov nucleic acid test was positive. 3.ct of the lung conformed to the manifestation of viral pneumonia.

inclusion criteria: 1.meet the definition of severe pneumonia(comply with any of the followings): shortness of breath,rr≥30 bpm; in a resting state:spo2≤93%; pao2/fio2≤300mmhg. 2.2019-ncov nucleic acid test was positive. 3.ct of the lung conformed to the manifestation of viral pneumonia.

inclusion criteria: 1.meet the definition of severe pneumonia(comply with any of the followings): 1. shortness of breath,rr≥30 bpm; 2. in a resting state:spo2≤93%; 3. pao2/fio2≤300mmhg. 2.2019-ncov nucleic acid test was positive. 3.ct of the lung conformed to the manifestation of viral pneumonia.

inclusion criteria: 1.meet the definition of severe pneumonia(comply with any of the followings): 1. shortness of breath,rr≥30 bpm; 2. in a resting state:spo2≤93%; 3. pao2/fio2≤300mmhg. 2.2019-ncov nucleic acid test was positive. 3.ct of the lung conformed to the manifestation of viral pneumonia.