72 patients admitted with COVID-19 pneumonia (39 men, 46.2 ± 15.9 years) were retrospectively analyzed. Three patients had uncomplicated illness, 61 patients had mild disease, and 8 patients had severe disease. Fourteen patients initially had negative nucleic acid tests that were subsequently positive. Patients had been admitted to the hospital for 4 to 27 days (median, 17 days). Thirty-two patients recovered and were discharged during the study period, and the median length of the clinical course was 15.5 days (range, 9 to 25 days). For those who remained hospitalized at the end of this investigation, the median length of hospitalization was 17.5 days (range, 4 to 27 days). No patient died during the study period. Among those with COVID-19, the severe patients were older than patients with mild and uncomplicated illness (P < 0.001).