Objective To analyze the epidemiological characteristics of influenza virus in severe acute respiratory tract infection (SARI) cases in Jingzhou City, so as to provide a scientific basis for the formulation of influenza prevention and control policies in Jingzhou City.

Methods SARI surveillance was carried out in two sentinel hospitals in Jingzhou City from 2018 to 2023. Respiratory tract samples were collected from cases and influenza virus nucleic acid was measured using real-time fluorescent polymerase chain reaction (RT-PCR).

Results A total of 2 603 SARI samples were tested from 2018 to 2023, and 338 samples were positive for influenza virus nucleic acid, with a detection rate of 12.99%. The highest positive detection rate was 20.22% in 2019, followed by 14.29% in 2022, and the lowest detection rate was 7.75% in 2020. There were significant differences for the positive detection rates of influenza in each monitoring year (χ²=30.386, P<0.001). There were epidemic peaks in the five surveillance years from 2018 to 2023 except 2020. There were winter epidemic peaks during 2018‒2019 and 2021‒2022, and an obvious summer epidemic peak was also observed from 2019 to 2022. H1N1, H3N2, B-Victoria and B-Yamagata were alternately prevalent in the six surveillance years. In 2019, H1N1, H3N2 and B-Victoria were alternately prevalent with time progress, in 2021 only B-Victoria was prevalent, and in 2022 H3N2 and B-Victoria were prevalent. There was no statistically significant difference for the positive detection rates of influenza virus between different genders (χ²=0.178, P=0.673). Among the four age groups, the positive rate of influenza virus in the age group of 15‒<25 years old was the highest (40.91%), followed by the age group of 25‒<60 years old (21.31%). There were statistically significant differences for the positive rates of influenza virus among different age groups (χ²=24.496, P<0.001).

Conclusion The surveillance of SARI cases in Jingzhou City could serve as an effective supplement to the surveillance of ILI in sentinel hospitals. It is suggested to expand the surveillance scope, strengthen public education and outreach on the prevention and control of respiratory diseases, thereby providing a scientific basis for influenza prevention and control.