An Epidemiological Analysis of Influenza Virus in The Context of COVID-19 Pandemic

Objective: The global health interventions implemented during the COVID-19 pandemic fundamentally altered the transmission of communicable diseases. This study examines changes in influenza virus epidemiology within the Turkish public health system across different phases of the pandemic. Methods: This retrospective study analyzed 3,585 pediatric patients (aged 0–18 years) diagnosed with influenza between January 2018 and June 2023. We stratified the cohort into three periods based on admission dates: pre-COVID-19, the COVID-19 pandemic, and the post-COVID-19 period. Results: We observed a statistically significant increase in the mean age of patients during the pandemic period (p<0.001). The incidence of influenza B decreased significantly during the pandemic compared to other periods (p<0.001). The post-pandemic period was characterized by higher viral co-infection rates and increased hospitalization frequencies (p<0.001), though the duration of hospitalization decreased during the pandemic (p<0.001). In the post-pandemic phase, the typical November surge was less pronounced, with peak incidence shifting to January. Conclusion: The pandemic significantly altered influenza epidemiology, shifting viral subtype prevalence, incidence rates, co-infection patterns, seasonal trends, and mortality risks.