Hospitals experiencing a COVID-19 outbreak are in a similar situation to those affected by natural disasters, with a breakdown in command and coordination, shortage of personnel and supplies, and increased stress among staff. In Japan, when a COVID-19 outbreak occurs, the first step is for the hospital or health center to respond. However, if the local authorities are unable to respond, the Ministry of Health, Labour and Welfare dispatch Disaster Medicine Assistance Team (DMAT) by request of the local government to facilitate early recovery. This study will examine the effectiveness of early phase support by DMAT.

Patients and healthcare workers in 31 hospitals supported by DMAT after an outbreak occurred between April 2020 and January 2021 were included in the study. Attack rate and case fatality rate for patients and the attack rate for healthcare workers were analyzed for each of the two groups: those that started support less than ten days after the first positive case and those that started support more than ten days after the first positive case.

For hospitals that started support in less than ten days, the attack rate was 27.9%, the case fatality rate was 17.4% for patients, and the attack rate for healthcare workers was 9.7%. For hospitals that took more than ten days to start support, the attack rate was 44.8%, the case fatality rate was 23.1% for patients, and the attack rate for healthcare workers was 14.3%. The attack rate (p<0.001) and case fatality rate (p=0.011) for patients and attack rate for healthcare workers (p<0.001) were significantly lower in hospitals that started support in less than ten days.

Early intervention of DMAT support using natural disaster support techniques for hospitals experiencing an outbreak reduced the attack rate and case fatality rate for patients and healthcare workers.