To monitor the epidemiological dynamics of influenza in Guizhou Province from 2022 to 2025 and analyze the resistance of influenza A (H1N1) pdm09 subtype viruses to neuraminidase inhibitors, so as to provide evidence for influenza prevention and control as well as clinical drug therapy.

Influenza-like illness (ILI) surveillance data from sentinel hospitals within Guizhou Province's national influenza surveillance network (2022—2025) were collected and analyzed using descriptive methods. Sixty-four influenza A (H1N1) pdm09 subtype viruses isolated and identified in Guizhou Province from 2022 to 2025 were selected. A fluorescence-based luminescence assay was employed to perform phenotypic drug resistance testing on the selected influenza viruses, and the changes in drug susceptibility to oseltamivir and zanamivir were analyzed. NA gene sequencing of the influenza strains was carried out, and bioinformatics software was used to analyze the amino acid site mutations of relevant drug-resistant genes.

Between 2022 and 2025, influenza viruses in Guizhou Province exhibited an alternating or co-circulation epidemic pattern. All 64 isolated A (H1N1) pdm09 subtype influenza virus strains were sensitive to oseltamivir and zanamivir. The mean IC₅₀ value for oseltamivir was 0.448 nmol/L (range: 0.126–1.013 nmol/L), and for zanamivir, it was 0.308 nmol/L (range: 0.112–0.855 nmol/L). Sequencing was performed on the NA genes of 46 A (H1N1) pdm09 strains. All sequenced viruses were classified into clade 6B.1 and were interspersed on the phylogenetic tree without forming distinct clusters. No mutations were identified at the enzyme active catalytic sites or known resistance sites in the NA gene.

From 2022 to 2025, influenza viruses in Guizhou Province showed an alternating or co-circulation pattern. The A (H1N1) pdm09 subtype remained sensitive to oseltamivir and zanamivir, supporting the continued clinical use of this drug class.