Etiological surveillance for influenza A in Inner Mongolia Autonomous Region, 2009−2022

Objective To analyze the etiological characteristics of Influenza A in Inner Mongolia Autonomous Region from 2009 to 2022 and provide scientific basis for the prevention and control of influenza epidemic in Inner Mongolia Autonomous Region.

Methods The etiological data of Influenza-like illness (ILI) from 2009 to 2022 were collected from 19 sentinel hospitals and 14 surveillance network laboratories in Inner Mongolia Autonomous Region for descriptive and statistical analyses.

Results From 2009 to 2020, A total of 134539 throat swabs from ILI cases were collected, of which 14626 were positive, with a positive rate of 10.87%, and a total of 9159 cases of influenza A were detected (62.62%) . The annual influenza virus subtypes or lineages alternated in winter and spring influenza season, with A (H3N2) being predominate. The positive rate of influenza A virus was highest in age group 5 years（9.31%）, and the positive rate of influenza A virus and the subtype varied in eastern, western and central Inner Mongolia Autonomous Region.

Conclusion The etiology of influenza A in Inner Mongolia Autonomous Region varied from year to year, showing obvious seasonality and population and area specific differences（ χ²=634.138, P＜0.05）. The incidence was high in winter and spring. It is necessary to strengthen the influenza prevention in students and vulnerable population by both influenza vaccination and non-pharmacological intervention to reduce the incidence of influenza.