COVID-19 (Coronavirus Disease 2019) Registry of University Hospital of Ioannina. Retrospective datasource registry with quantitative and qualitative patient data from the hospital medical records. Epidemiological, clinical and laboratory parameters are recorded on 7 different time points (day: 1, 3, 5, 7, 9, 11, 15) concerning 793 variables of interest in an electronic (computerised) database. Patients are also followed-up after 90 days from hospital discharge (number of visits of follow-up depends on patient's health status) at the Post-COVID and Long-term effects of coronavirus (long COVID) outpatient clinic of University Hospital of Ioannina. Data from this outpatient clinic are also recorded in an electronic database (189 variables of concern for each patient)