Japan recently experienced two major heavy rain disasters: the West Japan heavy rain disaster in July 2018 and the Kumamoto heavy rain disaster in July 2020. Between the occurrences of these two disasters, Japan began experiencing the wave of the coronavirus disease 2019 (COVID-19) pandemic, providing a unique opportunity to compare the incidence of acute respiratory infection (ARI) between the two disaster responses under distinct conditions.

The data were collected by using the standard disaster medical reporting system used in Japan, so-called the Japan-Surveillance in Post-Extreme Emergencies and Disasters (J-SPEED), which reports number and types of patients treated by Emergency Medical Teams (EMTs). Data for ARI were extracted from daily aggregated data on the J-SPEED form and the frequency of ARI in two disasters was compared.

Acute respiratory infection in the West Japan heavy rain that occurred in the absence of COVID-19 and in the Kumamoto heavy rain that occurred in the presence of COVID-19 were responsible for 5.4% and 1.2% of the total consultation, respectively (P <.001).

Between the occurrence of these two disasters, Japan implemented COVID-19 preventive measures on a personal and organizational level, such as wearing masks, disinfecting hands, maintaining social distance, improving room ventilation, and screening people who entered evacuation centers by using hygiene management checklists. By following the basic prevention measures stated above, ARI can be significantly reduced during a disaster.