Retrospective Epidemiological Analysis of Influenza A Infections in a Single Hospital in Korea (2007–2024): Age, Sex, and Seasonal Patterns

Influenza A is a respiratory virus that causes high infection rates and mortality worldwide, particularly affecting high-risk groups such as children, older adults, and individuals with chronic conditions. This retrospective study was conducted at a single tertiary hospital in Korea to analyze the epidemiological characteristics of influenza A infections from 2007 to 2024, focusing on age, sex, and seasonal variations. Using multiplex real-time PCR data from 23,284 individuals, we found that the overall positivity rate for influenza A was 5.6%, with seasonal fluctuations showing the highest rate in winter (14.0%) and the lowest in summer (0.5%). Age-based analysis revealed significantly higher positivity rates in older adults (7.9%) and adults (7.6%) than in children (5.0%) and infants (3.1%). No significant differences were observed in positivity rates between sexes (male: 5.43%, female: 5.76%, <i>p</i> = 0.428). These findings provide essential insights into the regional and seasonal patterns of influenza A, emphasizing the importance of targeted vaccination strategies, adaptive public health interventions, and continuous surveillance for effective prevention and outbreak control management.