Objective:To analyze the epidemic trend of influenza-like illness（ILI）cases，etiological detection results，and the evolution of the hemagglutinin（HA）gene of the predominant strains in Hanzhong City，Shaanxi Province during the 2018-2024 influenza seasons.Methods:ILI sentinel surveillance data and network laboratory test results during the 2018-2024 influenza seasons in Hanzhong City，Shaanxi Province were collected for descriptive analysis. The HA gene sequences of 25 predominant strains were obtained through whole-genome deep sequencing method，and then compared with the vaccine strains recommended by the World Health Organization in the same period to analyze the evolution of the virus.Results:A total of 37 770 cases of ILI were reported in Hanzhong City during the 2018-2024 influenza seasons，and the proportion of total ILI cases（ILI%）was 2.87%（37 770/1 316 009）. The epidemic trend of ILI showed an obvious epidemic peak in winter and spring（from December of the current year to March of the following year）. The specimens with the highest positive rate were of type A（H3N2）（39.12%，365/933），and the predominant epidemic strains in each influenza season alternated among A（H1N1）pdm09（in the 2018-2019 and 2022-2023 influenza seasons），A（H3N2）（in the 2019-2020 and 2023-2024 influenza seasons）and B（Victoria）（in the 2021-2022 influenza season）. The phylogenetic relationship gradually became more distant over time across different influenza seasons. Among them，the epidemic strains of A（H1N1）pdm09 belonged to the 6B.1 clade，and the evolution mainly occurred in the Sa and Sb regions of the HA epitope. Meanwhile，the epidemic strains of A（H3N2）belonged to the 3C clade，and the evolution mainly took place in the A，B and C regions of the HA epitope. The strains of the B（Victoria）lineage belonged to the V1a.3a.2 clade，and the evolution mainly occurred in the 120-loop，150-loop，and 190-helix regions of the HA epitope.Conclusions:The influenza epidemic in Hanzhong City has obvious seasonality，and the amino acids of the epidemic strains have shown a certain degree of variation over the years. In future prevention and control work，influenza surveillance should be continuously strengthened，and the change trend of the predominant circulating strains should be closely monitored.

Objective:To analyze the epidemic trend of influenza-like illness（ILI）cases，etiological detection results，and the evolution of the hemagglutinin（HA）gene of the predominant strains in Hanzhong City，Shaanxi Province during the 2018-2024 influenza seasons.Methods:ILI sentinel surveillance data and network laboratory test results during the 2018-2024 influenza seasons in Hanzhong City，Shaanxi Province were collected for descriptive analysis. The HA gene sequences of 25 predominant strains were obtained through whole-genome deep sequencing method，and then compared with the vaccine strains recommended by the World Health Organization in the same period to analyze the evolution of the virus.Results:A total of 37 770 cases of ILI were reported in Hanzhong City during the 2018-2024 influenza seasons，and the proportion of total ILI cases（ILI%）was 2.87%（37 770/1 316 009）. The epidemic trend of ILI showed an obvious epidemic peak in winter and spring（from December of the current year to March of the following year）. The specimens with the highest positive rate were of type A（H3N2）（39.12%，365/933），and the predominant epidemic strains in each influenza season alternated among A（H1N1）pdm09（in the 2018-2019 and 2022-2023 influenza seasons），A（H3N2）（in the 2019-2020 and 2023-2024 influenza seasons）and B（Victoria）（in the 2021-2022 influenza season）. The phylogenetic relationship gradually became more distant over time across different influenza seasons. Among them，the epidemic strains of A（H1N1）pdm09 belonged to the 6B.1 clade，and the evolution mainly occurred in the Sa and Sb regions of the HA epitope. Meanwhile，the epidemic strains of A（H3N2）belonged to the 3C clade，and the evolution mainly took place in the A，B and C regions of the HA epitope. The strains of the B（Victoria）lineage belonged to the V1a.3a.2 clade，and the evolution mainly occurred in the 120-loop，150-loop，and 190-helix regions of the HA epitope.Conclusions:The influenza epidemic in Hanzhong City has obvious seasonality，and the amino acids of the epidemic strains have shown a certain degree of variation over the years. In future prevention and control work，influenza surveillance should be continuously strengthened，and the change trend of the predominant circulating strains should be closely monitored.