inclusion criteria: willing and able to provide written informed consent prior to performing study procedures age ≥18 years, and ≤75 years; a confirmed case of covid-19. the criteria are as follows: clinically diagnosed or suspected cases with one of the following etiological evidence: 1) sars-cov-2 nucleic acid is positive in respiratory or blood samples detected by rt-pcr; 2) virus sequence detected in respiratory or blood samples shares high homology with the known sequence of sars-cov-2. clinical classification is severe case: meet any of the following: 1) increased respiratory rate (≥30 beats / min), difficulty breathing, cyanosis of the lips; 2) peripheral capillary oxygen saturation (spo2) ≤93% at rest ; 3)partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤300 mmhg (1mmhg = 0.133kpa).

inclusion criteria: willing and able to provide written informed consent prior to performing study procedures age ≥18 years, and ≤75 years; a confirmed case of covid-19. the criteria are as follows: clinically diagnosed or suspected cases with one of the following etiological evidence: 1) sars-cov-2 nucleic acid is positive in respiratory or blood samples detected by rt-pcr; 2) virus sequence detected in respiratory or blood samples shares high homology with the known sequence of sars-cov-2. clinical classification is severe case: meet any of the following: 1) increased respiratory rate (≥30 beats / min), difficulty breathing, cyanosis of the lips; 2) peripheral capillary oxygen saturation (spo2) ≤93% at rest ; 3)partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤300 mmhg (1mmhg = 0.133kpa).

inclusion criteria: 1. willing and able to provide written informed consent prior to performing study procedures 2. age ≥18 years, and ≤75 years; a confirmed case of covid-19. the criteria are as follows: clinically diagnosed or suspected cases with one of the following etiological evidence: 1) sars-cov-2 nucleic acid is positive in respiratory or blood samples detected by rt-pcr; 2) virus sequence detected in respiratory or blood samples shares high homology with the known sequence of sars-cov-2. 3. clinical classification is severe case: meet any of the following: 1) increased respiratory rate (≥30 beats / min), difficulty breathing, cyanosis of the lips; 2) peripheral capillary oxygen saturation (spo2) ≤93% at rest ; 3)partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤300 mmhg (1mmhg = 0.133kpa).

inclusion criteria: 1. willing and able to provide written informed consent prior to performing study procedures 2. age ≥18 years, and ≤75 years; a confirmed case of covid-19. the criteria are as follows: clinically diagnosed or suspected cases with one of the following etiological evidence: 1) sars-cov-2 nucleic acid is positive in respiratory or blood samples detected by rt-pcr; 2) virus sequence detected in respiratory or blood samples shares high homology with the known sequence of sars-cov-2. 3. clinical classification is severe case: meet any of the following: 1) increased respiratory rate (≥30 beats / min), difficulty breathing, cyanosis of the lips; 2) peripheral capillary oxygen saturation (spo2) ≤93% at rest ; 3)partial pressure of arterial oxygen (pao2) / fraction of inspired oxygen (fio2) ≤300 mmhg (1mmhg = 0.133kpa).