What Caused Dire Clusters ? ~Analysis of Nosocomial COVID-19 Outbreaks in Kyoto City, Japan From the 1st Wave Through 3rd Wave in 2020/21

Fifteen COVID-19 nosocomial clusters occurred in the first year of the pandemic in Kyoto City, involving 232 in-hospital patients and 157 healthcare workers (HCWs). Among them, 40 percent of index cases were HCWs. The in-hospital mortality rate among patients was 18.1%, whereas the mortality rate in the Kyoto City area during the study period was 1.79%. The time needed to contain outbreaks was shorter in hospitals with full-time infection control personnel assigned.