Changes in the epidemiological characteristics of influenza in children in Zhengzhou, China, in the post-COVID-19 era.

Background: Influenza is a contagious respiratory disease posing a huge burden of disease for children around the world. The purpose of this study was to investigate the epidemiologic changes in childhood influenza in Zhengzhou, China, before, during, and after the COVID-19 outbreak. The aim of this study was to determine the impact of the COVID-19 outbreak and related prevention and control policies on the children's influenza epidemiological trend.

Methods: All influenza report card data from the Children's Hospital Affiliated with Zhengzhou University's Disease Surveillance Reporting Management System were collected and analyzed monthly from January 2018 to December 2023. The period of the study was divided into three phases for comparison: the pre-pandemic period, the pandemic period, and the post-pandemic period.

Results: Between January 2018 and December 2023, a total of 82,030 children with influenza were diagnosed at our hospital, including 46,453 males and 35,577 females. A total of 11,833 of them had to be hospitalized for influenza, and 321 of them were brought to the ICU. Influenza showed low-level epidemiologic status during the COVID-19 pandemic, and there was a substantial rise in influenza and a surge in the number of cases after the COVID-19 pandemic period. The year 2023 will had the most influenza cases (40,785). The peak incidence of influenza changes in 2022, from July to October, and in 2023, from February to April and from October to December. During the post-pandemic period, the proportion of new-borns and young children among influenza patients decreased, while the proportion of school-age children increased significantly, and the proportion of influenza patients hospitalized and the proportion of ICU admissions decreased.

Conclusion: Influenza showed low-level epidemiologic status during the COVID-19 pandemic. In the post-pandemic period, there is a large increase in influenza incidence, with a double peak in influenza incidence. The proportion of school-age children with influenza has also increased. As a result, we recommend that influenza vaccination for key populations, particularly school-age children, be completed by October of each year in Henan Province, and that the government and schools increase education about nonpharmacological influenza prevention approaches.