Purpose: In Korea, seasonal influenza is an important respiratory illness afflicting children every year. We aimed to investigate the childhood epidemiology in Jeju during the 2017-2018 and 2018-2019 seasons. Methods: Children aged <13 years, who were tested for influenza at the Jeju National University Hospital during the 2017-2018 and 2018-2019 influenza seasons, were included. Demographics and the influenza test results were retrospectively reviewed from their medical records. Results: This

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... tudy included 5,219 cases of influenza-like illness (ILI) (2017-2018: n=2,279; 2018-2019: n=2,940). The mean age of the eligible children was 2.85±2.79 years, and the most common age among ILI patients in each season was 1 year group. There were 902 (17.3%, 902/5,219) confirmed influenza cases during the 2 seasons. The rate of influenza confirmed by rapid influenza diagnostic test or polymerase chain reaction among ILI patients in the 2017-2018 and 2018-2019 seasons was 10.4% (236/2,279) and 10.3% (303/2,940) for influenza A, and 9.1% (208/2,279) and 5.3% (155/2,940) for influenza B, respectively. The mean age of influenza-confirmed cases was 4.09 years and 5.05 years in the 2017-2018 and 2018-2019 seasons, respectively (P<0.05). Weekly distribution of influenza was similar to that of ILI in the clinical sentinel surveillance system in both seasons. Conclusion: The difference in the influenza epidemic trend and age-group distribution between the 2017-2018 and 2018-2019 seasons was distinct in Jeju. Steady epidemiological studies on influenza in Jeju are needed for comparison with other regions of Korea.