tetano
Editor, Senior Moderator
J Epidemiol
. 2026 Jan 10.
doi: 10.2188/jea.JE20250453. Online ahead of print. Resurgence of Influenza following the lifting of non-pharmaceutical interventions in Shenzhen, China
Zhenhu Chen[SUP] 1 2 3 [/SUP], Xiujuan Tang[SUP] 4 [/SUP], Hui Liu[SUP] 4 [/SUP], Weihua Wu[SUP] 4 [/SUP], Ying Sun[SUP] 4 [/SUP], Min Jiang[SUP] 4 [/SUP], Xin Wang[SUP] 4 [/SUP], Xuan Zou[SUP] 4 [/SUP], Li Li[SUP] 3 [/SUP], Jinjun Ran[SUP] 5 [/SUP], Shengzhi Sun[SUP] 6 [/SUP], Shi Zhao[SUP] 7 [/SUP], Shisong Fang[SUP] 4 [/SUP], Peihua Cao[SUP] 1 2 3 [/SUP]
Affiliations
Background: During the COVID-19 pandemic, global influenza activity sharply declined due to extensive non-pharmaceutical interventions (NPIs). Understanding how influenza activity rebounded after these interventions were lifted is critical for informing future respiratory virus control strategies.
Methods: We conducted a descriptive analysis of the temporal characteristics of weekly number of influenza-like illness (ILI) cases, ILI%, influenza-positive cases, and influenza-positive rates. Poisson log-link regression models, incorporating meteorological factors using data from 2013 to 2019, were established to predict the weekly influenza-positive rate under a counterfactual scenario without COVID-19 interventions in 2022-2023.
Results: Our findings indicate that the cancellation of COVID-related non-pharmacological interventions (NPIs) had a notable impact on increasing influenza transmission. Children under 5 years old exhibited the highest ILI cases. The influenza positivity rate surged to 34.35% during the pandemic relaxation, surpassing pre-pandemic (24.53%) and pandemic (9.56%) rates. During the pre-COVID-19 period, various influenza virus subtypes were co-circulated, with the predominant subtype varying. However, during the COVID-19 pandemic period, the dominant strains were influenza A/H1N1 and influenza B/Victoria lineage, while influenza A/H3N2 predominated in the pandemic relaxation period.
Conclusion: The marked resurgence of influenza activity in Shenzhen following the lifting of COVID-related NPIs underscores the need for sustained surveillance and preparedness for concurrent or sequential respiratory virus outbreaks.
Keywords: COVID-19; influenza; non-pharmacological interventions (NPIs); resurgence.
. 2026 Jan 10.
doi: 10.2188/jea.JE20250453. Online ahead of print. Resurgence of Influenza following the lifting of non-pharmaceutical interventions in Shenzhen, China
Zhenhu Chen[SUP] 1 2 3 [/SUP], Xiujuan Tang[SUP] 4 [/SUP], Hui Liu[SUP] 4 [/SUP], Weihua Wu[SUP] 4 [/SUP], Ying Sun[SUP] 4 [/SUP], Min Jiang[SUP] 4 [/SUP], Xin Wang[SUP] 4 [/SUP], Xuan Zou[SUP] 4 [/SUP], Li Li[SUP] 3 [/SUP], Jinjun Ran[SUP] 5 [/SUP], Shengzhi Sun[SUP] 6 [/SUP], Shi Zhao[SUP] 7 [/SUP], Shisong Fang[SUP] 4 [/SUP], Peihua Cao[SUP] 1 2 3 [/SUP]
Affiliations
- PMID: 41526273
- DOI: 10.2188/jea.JE20250453
Background: During the COVID-19 pandemic, global influenza activity sharply declined due to extensive non-pharmaceutical interventions (NPIs). Understanding how influenza activity rebounded after these interventions were lifted is critical for informing future respiratory virus control strategies.
Methods: We conducted a descriptive analysis of the temporal characteristics of weekly number of influenza-like illness (ILI) cases, ILI%, influenza-positive cases, and influenza-positive rates. Poisson log-link regression models, incorporating meteorological factors using data from 2013 to 2019, were established to predict the weekly influenza-positive rate under a counterfactual scenario without COVID-19 interventions in 2022-2023.
Results: Our findings indicate that the cancellation of COVID-related non-pharmacological interventions (NPIs) had a notable impact on increasing influenza transmission. Children under 5 years old exhibited the highest ILI cases. The influenza positivity rate surged to 34.35% during the pandemic relaxation, surpassing pre-pandemic (24.53%) and pandemic (9.56%) rates. During the pre-COVID-19 period, various influenza virus subtypes were co-circulated, with the predominant subtype varying. However, during the COVID-19 pandemic period, the dominant strains were influenza A/H1N1 and influenza B/Victoria lineage, while influenza A/H3N2 predominated in the pandemic relaxation period.
Conclusion: The marked resurgence of influenza activity in Shenzhen following the lifting of COVID-related NPIs underscores the need for sustained surveillance and preparedness for concurrent or sequential respiratory virus outbreaks.
Keywords: COVID-19; influenza; non-pharmacological interventions (NPIs); resurgence.