key: cord-0948330-dz2oikdh authors: 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 title: Reduction of Influenza in Osaka, Japan During the COVID-19 Outbreak: A Population-based ORION Registry Study date: 2021-10-14 journal: IJID Regions DOI: 10.1016/j.ijregi.2021.10.002 sha: 67eec9974d92f9649cb1343354dc5c697600351a doc_id: 948330 cord_uid: dz2oikdh 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. Tel: +81-6-6879-5707; Fax: +81-6-6879-5720 E-mail: htomoya1979@hp-emerg.med.osaka-u.ac.jp The global outbreak of coronavirus disease has resulted in various prevention and control measures being implemented globally to control its spread (Yanase et al., 2021; Daemi et al. 2021) . Although the spread of COVID-19 affected the incidence of other infectious diseases, there are no reports evaluating the impact of COVID-19 on influenza incidence using comprehensive regional population-based data. The Osaka Prefecture Government developed an information system for emergency patients transported by emergency medical service (EMS) personnel called the Osaka Emergency Information Research Intelligent Operation Network (ORION) system, which compiles prehospital ambulance records and in-hospital information such as diagnosis and prognosis (Okamoto et al., 2019) . In the present study, we attempted to evaluate the impact of COVID-19 on the incidence of influenza using the population-based ORION registry. This was a retrospective observational study using the ORION database (Okamoto et al., 2019) . The study period spanned 3 year from 2018 to 2020. Osaka Prefecture is located in the western area of Japan, covers an area of 1905 km 2 , and has a population of 8.8 million served by 519 hospitals (106,273 beds) (Okamoto et al., 2019) . Classification of Diseases and Related Health Problems) 10 codes such as J09, Influenza due to certain identified influenza viruses; J10, Influenza due to other identified influenza virus; and J11, Influenza due to unidentified influenza virus. The influenza incidence rate ratio (IRR) and associated 95% confidence interval (CI) were calculated based on a previous study (Maeda et al. 2021 The first confirmed cases of COVID-19 infection in Osaka, Japan were reported in January 2020. Figure 1 shows the weekly number of influenza patients in Osaka Prefecture between 2018 and 2020. From January 2020, the number of influenza patients dramatically decreased, and almost no influenza patients were recognized in the winter of 2020. Table 1 shows the monthly incidence and IRR of the influenza patients. The IRR values show that the decrease in influenza patients in 2020 was remarkable (IRR 2020/2018 0.39 [95% CI 0.37-0.41]). Influenza is a well-known highly contagious viral infection that has been responsible for the death of many people over the history of pandemics (Daemi et al. 2021 ). However, our analysis of the population-based ORION registry in Osaka, Japan revealed a reduction of influenza in Japan during the COVID-19 outbreak. countries and areas during the COVID-19 pandemic (Sawakami et al., 2021) . Further, influenza outbreaks have declined since the COVID-19 pandemic began using national reports from sentinel surveillance in Japan (Sawakami et al., 2021 , Sakamoto et al. 2020 ). Our study using the comprehensive regional ORION database showed the same result. Possible reasons for the reduction in influenza may be that 1) influenza viral infection is less infectious than COVID-19 (Biggerstaff et al., 2014 , Locatelli et al. 2021 , Mir and Koul, 2021 and 2) social distancing, intermittent lockdowns, closure of schools, and restrictions on mass gatherings were effective. Similar reports have been published in other countries, and we will continue to follow this trend in the future (Mir and Koul, 2021, Olsen et al 2020) . The monthly IRR had already decreased in January 2020, although the first confirmed case of COVID-19 in Osaka was reported in January 2020. During this period, infection controls such as closure of schools and restriction on mass gatherings had not started, and the attitude of citizens toward the prevention of infection had not been changed in Japan. However, COVID-19 might have slightly altered the attitude of citizens toward the prevention of infection in January 2020 because information on COVID-19 was already being reported worldwide, especially from China. This study has limitations. First, it included only influenza patients evaluated by EMS personnel and did not include walk-in patients. Second, only data collected after 2018 when ORION was developed were included, and thus they cannot be compared with data prior to 2018. However, sentinel surveillance data of influenza in Osaka 9 Prefecture including data of walk-in patients and data prior to 2018 showed the same trend as the findings from our study (Osaka Institute of Public Health, 2021). Thus, the ORION database could provide important information about emergency patients with influenza similar to that of sentinel surveillance. From January 2020 when the first confirmed cases of COVID-19 infection were reported in Osaka, Japan, the number of influenza patients decreased in a comprehensive regional analysis using the population-based ORION registry. YKatayama and TK designed study. TH, YKatayama, KT, ShunichiroNakao, JT and TK analyzed data. MN, TI, SF, TU, YMiyamoto, TB, TMizobata, YKuwagata, TS and TM supervised this research project. TH wrote the first draft. All of the authors read and approved the final manuscript. This study was approved by the Ethics Committee of the Osaka University Graduate School of Medicine (No. 15003). This study was supported by the Japan Society of the Promotion of Science KAKENHI [grant number 21K09071]. All authors report no conflicts of interest. Estimates of the reproduction number for seasonal, pandemic, and zoonotic influenza: a systematic review of the literature Progression and trends in virus from influenza A to COVID-19: an overview of recent studies Estimating the basic reproduction number for COVID-19 in Western Europe Changes in percutaneous coronary intervention practice in Japan during the COVID-19 outbreak: LIFE Study Profile of the ORION (Osaka emergency information Research Intelligent Operation Network system) between Decreased influenza activity during the COVID-19 pandemic -United States Seasonal influenza activity during the SARS-CoV-2 outbreak in Japan Infectious disease activity during the COVID-19 epidemic in Japan: Lessons learned from prevention and control measures Prevalence of COVID-19 and the continued citizen-based control in Japan Sentinel surveillance diseases -Comparison of past data by disease-2021 The authors thank the EMS personnel, nurses, and emergency physicians who participated in ORION. We thank our colleagues from Osaka University Center of Project for providing their insight and expertise for our research. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.