Reduction of Influenza in Osaka, Japan During the COVID-19 Outbreak: A Population-based ORION Registry Study

Hirose, Tomoya; Katayama, Yusuke; Tanaka, Kenta; Kitamura, Tetsuhisa; Nakao, Shunichiro; Tachino, Jotaro; Nakao, Shota; Nitta, Masahiko; Iwami, Taku; Fujimi, Satoshi; Uejima, Toshifumi; Miyamoto, Yuji; Baba, Takehiko; Mizobata, Yasumitsu; Kuwagata, Yasuyuki; Shimazu, Takeshi; Matsuoka, Tetsuya

Objectives The spread of COVID-19 has affected the incidence of other infectious diseases, but there are no reports evaluating the impact of COVID-19 on influenza incidence using comprehensive regional population-based data. We attempted to evaluate the impact of COVID-19 on influenza using the population-based ORION (Osaka Emergency Information Research Intelligent Operation Network) registry. Methods Osaka Prefecture developed the ORION registry of emergency patients treated by emergency medical service (EMS) personnel. We included emergency patients with influenza using the ICD (International Statistical Classification of Diseases and Related Health Problems) 10 codes. Influenza incidence rate ratio (IRR) and associated 95% confidence interval (CI) were calculated. Results The numbers of influenza patients transported by EMS decreased during the COVID-19 pandemic. The IRR showed the decrease in influenza patients in 2020 to be remarkable (IRR 2020/2018 0.39, 95% CI 0.37–0.41). Conclusions From January 2020 when the first confirmed cases of COVID-19 infection were reported in Osaka, Japan, the number of influenza patients transported decreased in a comprehensive regional analysis using the population-based ORION registry.