Study design and patients
We retrospectively recruited 55 patients who were diagnosed as COVID-19 pneumonia at the Zhongnan Hospital of Wuhan University from Jan. 8, 2020 to Feb. 10, 2020. The patients comprised 19 males and 36 females with a median age of 37 (range 22–67 years). Diagnosis of COVID-19 pneumonia was based on the New Coronavirus Pneumonia Prevention and Control Program. All patients with COVID-19 pneumonia were tested positively for SARS-CoV-2 by use of quantitative RT-PCR on samples from the respiratory tract. This study was reviewed and approved by the Ethical Committee of Zhongnan Hospital of Wuhan University. Written informed consent was waived by the Ethics Commission for emerging infectious diseases.