Suspected flu cases appear because everyone is not wearing masks

(1)Number per 1000 unit of trend of suspected school-age flu cases by year
(2)7 to 12 years old
(3)13 to 18 years old
(4)2018 2019 2020 2021 2022 2023
(5)Data from the Korea Centers for Disease Control and Prevention as of the 4th week of September