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Background <p>Respiratory infections, particularly those caused by influenza A virus (IAV), represent a major global health concern, contributing to substantial morbidity, mortality, and economic burden on healthcare systems worldwide.</p> Methods <p>We conducted a retrospective cohort study of 21,191 patient records in Chongqing, spanning a five-year surveillance period. Logistic and Poisson regression analyses were performed to characterize IAV prevalence across age-stratified, gender-specific, and clinically defined subgroups. In addition, restricted cubic spline (RCS) models were applied to examine the nonlinear effects of meteorological factors on IAV transmission.</p> Results <p>The overall IAV positivity rate was 13.79%, with marked differences across demographic subgroups. Preschool children (ages 4–6) showed the strongest association with IAV infection (OR = 6.25, 95% CI: 4.98–7.85; RR = 5.14, 95% CI: 4.13–6.41; both <i>P</i> &lt; 0.001), followed by school-aged children (ages 7–18; OR = 5.60, 95% CI: 4.45–7.06; RR = 4.70, 95% CI: 3.76–5.88; both <i>P</i> &lt; 0.001). Following the relaxation of COVID-19 restrictions, IAV positivity rebounded to 21.66% in 2023, with epidemic peaks observed in March–April and November–March. Four distinct epidemic waves were identified during the 2020–2024 surveillance period. RCS models revealed significant nonlinear associations between IAV prevalence and mean temperature, temperature variation, and mean relative humidity (all P for overall and nonlinear &lt; 0.05). The highest positivity rates occurred at mean temperatures of 7.16–16.80 °C, temperature differences &gt; 10.92 °C, and relative humidity levels of 61.91–74.00% (all <i>P</i> &lt; 0.05). Furthermore, IAV infection was significantly more common in female patients compared with male patients (14.79% vs. 12.57%), and among patients with upper respiratory tract infections compared with those with lower respiratory tract infections (15.84% vs. 11.42%).</p> Conclusions <p>These findings highlight the importance of targeted public health interventions and sustained surveillance to reduce the burden of IAV-related respiratory infections and improve patient outcomes.</p>

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Epidemiological characteristics of influenza A virus infection across age groups: a longitudinal analysis based on gender and clinical diagnosis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月16日

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  • Shu Li,
  • Kewei Xing,
  • Yan Su,
  • Xinyuan Zhang,
  • Chunli Li

摘要

Background

Respiratory infections, particularly those caused by influenza A virus (IAV), represent a major global health concern, contributing to substantial morbidity, mortality, and economic burden on healthcare systems worldwide.

Methods

We conducted a retrospective cohort study of 21,191 patient records in Chongqing, spanning a five-year surveillance period. Logistic and Poisson regression analyses were performed to characterize IAV prevalence across age-stratified, gender-specific, and clinically defined subgroups. In addition, restricted cubic spline (RCS) models were applied to examine the nonlinear effects of meteorological factors on IAV transmission.

Results

The overall IAV positivity rate was 13.79%, with marked differences across demographic subgroups. Preschool children (ages 4–6) showed the strongest association with IAV infection (OR = 6.25, 95% CI: 4.98–7.85; RR = 5.14, 95% CI: 4.13–6.41; both P < 0.001), followed by school-aged children (ages 7–18; OR = 5.60, 95% CI: 4.45–7.06; RR = 4.70, 95% CI: 3.76–5.88; both P < 0.001). Following the relaxation of COVID-19 restrictions, IAV positivity rebounded to 21.66% in 2023, with epidemic peaks observed in March–April and November–March. Four distinct epidemic waves were identified during the 2020–2024 surveillance period. RCS models revealed significant nonlinear associations between IAV prevalence and mean temperature, temperature variation, and mean relative humidity (all P for overall and nonlinear < 0.05). The highest positivity rates occurred at mean temperatures of 7.16–16.80 °C, temperature differences > 10.92 °C, and relative humidity levels of 61.91–74.00% (all P < 0.05). Furthermore, IAV infection was significantly more common in female patients compared with male patients (14.79% vs. 12.57%), and among patients with upper respiratory tract infections compared with those with lower respiratory tract infections (15.84% vs. 11.42%).

Conclusions

These findings highlight the importance of targeted public health interventions and sustained surveillance to reduce the burden of IAV-related respiratory infections and improve patient outcomes.