Abstract
The pathogenicity of SARS-CoV-2 has changed as the virus mutates, with some variants causing waves of new infections. We investigated the pathogenic changes in the virus during waves 3, 4, and 5 in terms of severity, treatment methods, and outcomes in 208 patients with COVID-19 admitted to our hospital. Maximum severity during hospitalization tended to increase in patients with moderate I and II COVID-19 during waves 4 and 5; however, the number of severe cases decreased. Comparison by propensity score matching revealed that the number of patients with moderate I and II COVID-19 also increased significantly during wave 5.
