This is a multicenter, ambispective observational cohort study. The patients with corona virus disease 2019 (COVID-19) will be included in the study. The patients will be divided into 4 groups according to the treatment mode (Azvudine treatment group within 48 hours after the first positive for nucleic acid, Azvudine treatment group after 48 hours after the first positive for nucleic acid, short course of Azvudine treatment without nucleic acid turning negative, and the control group) . This study aims to analyze the efficacy and safety of Azvudine in the treatment of patients with COVID-19.

Inclusion Criteria:

• Patients with confirmed diagnosis of COVID-19 pneumonia
• Patients with the ability to take medication orally

Exclusion Criteria:

• Severe vomiting and difficulty in taking oral medication or ingestion of drugs after oral administration
• Suspected or confirmed active systemic infection other than COVID-19 pneumonia
• Pregnant or lactating women
• Patients with mental disorders
• Patients with severe liver damage
• Patients who are treated with small molecule drugs such as Nirmatrelvir Tablets/Ritonavir Tablets(co-packaged)
• Patients who are treated with RNA-dependent RNA polymerase (RDRP) inhibitors (Junshipharma VV116, Ascletis Pharma Inc. Asc10, Kexing biopharm Shen26, and Molnupiravir).

All the patients who were diagnosed as COVID-19 pneumonia will be included in the study.