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Review
. 2025 Oct 17;22(1):335.
doi: 10.1186/s12985-025-02959-5.

Analysis of epidemiological characteristics of influenza viruses in Fengdu district, Chongqing, China, from 2022 to 2024

Ping Huang  1 , Xiaoqin Jiang  2 , Yuhong Liao  2
Affiliations
Review

Analysis of epidemiological characteristics of influenza viruses in Fengdu district, Chongqing, China, from 2022 to 2024

Ping Huang et al. Virol J. .

Abstract

Objective: To analyze the epidemiological characteristics of influenza viruses in Fengdu, Chongqing, and provide a scientific basis for influenza prevention and control in the region.

Methods: Pharyngeal swab samples were collected from influenza-like illness cases at Fengdu Traditional Chinese Medicine Hospital from 2022 to 2024 for etiological testing. Virus positivity rates across different years, genders, and occupations were compared, along with inflammatory indicators such as blood routine parameters between influenza A and B virus infections.

Results: A total of 19,576 nasopharyngeal swab samples were tested from 2022 to 2024, with 5073 positive for influenza viruses (detection rate: 25.91%). There were significant differences in positivity rates across different years (P < 0.001). The peak positivity rate for influenza A virus occurred in 2022 (27.15%), while influenza B virus had its highest detection rate in 2024 (5.67%). The epidemic peak for influenza A was from December to April of the following year, dominated by the H3N2 subtype; for influenza B, the peak was from December to March, with the Victoria lineage as the predominant strain. In terms of age distribution, the highest positivity rate for influenza A was observed in school-aged children aged 6 ~ 13 years (23.12%), while influenza B predominantly affected individuals aged 45 ~ 59 years (3.61%). Among different occupations, students had significantly higher positivity rates for both influenza A and B compared to other occupations (P < 0.05). The influenza A group had higher white blood cell count (WBC), neutrophil count (NC), neutrophil-to-lymphocyte ratio (NLR), C-reactive protein (CRP), and serum amyloid A (SAA) levels than the influenza B group (P < 0.05).

Conclusion: In Fengdu County, Chongqing, influenza epidemics exhibit distinct winter-spring seasonal patterns. Surveillance data indicate that influenza A (H3N2) constitutes the predominant subtype among type A viruses, while Victoria lineage dominates influenza B circulation. Epidemiological analysis reveals school-aged children demonstrate particular susceptibility to influenza A infections, whereas middle-aged adults show heightened vulnerability to influenza B. Public health recommendations emphasize: targeted vaccination campaigns for high-risk populations, enhanced health education initiatives, and utilization of inflammatory biomarkers to facilitate early differential diagnosis.

Keywords: Influenza a virus; Influenza b Virus; Influenza-Like illness (ILI) Cases; Epidemiology.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The portion of this study involving human subjects has been approved by the Ethics Committee of Fengdu County Traditional Chinese Medicine Hospital, Chongqing, China. All procedures adhered to the ethical standards outlined in the 1964 Helsinki Declaration and its subsequent amendments. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Temporal Distribution of Influenza Virus Infections from January 2022 to December 2024(Note: The Y-axis represents the number of positive cases.)
Fig. 2
Fig. 2
Subtype Distribution of Influenza Viruses from December 2023 to December 2024
See this image and copyright information in PMC

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