Fig. 2

Survival analysis using Kaplan–Meier survival curves. We used Kaplan–Meier survival curves to analyze outcomes of inpatients and outpatients during the hospitalization period. We assessed the occurrence rates of the a one-step progression of severity, b development to severe grade, and c death during the entire hospitalization. We performed a Log-rank test, and differences were considered significant when p < 0.05. IP, inpatient group; OP, outpatient group