Influenza and other respiratory viruses
Bidirectional Synergistic Interaction Between Influenza Virus and SARS-CoV-2 in the Postpandemic Era: A Modeling Study
By Qin Z, Wei Y, Zhou J and 4 others.
Abstract
Introduction
Influenza and COVID-19 are major respiratory diseases whose co-circulation dynamics are not fully understood. Surveillance data from the postpandemic period, free from the confounding effects of nonpharmaceutical interventions (NPIs), provide a unique opportunity to study their interactions. This study aimed to (1) estimate the direction and strength of the epidemiological interactions between influenza virus and SARS-CoV-2 and (2) quantify the impact of these interactions on the cumulative disease burden.
Methods
We developed a deterministic influenza virus × SARS-CoV-2 12-compartmental model SIR × SEIR using weekly laboratory surveillance data from Hong Kong between 2023 and 2025. Interaction parameters were introduced across multiple pathways to quantify the effect of one virus on the transmission of the other. Model parameters were estimated via maximum likelihood estimation (MLE), with uncertainty assessed using bootstrap resampling. Counterfactual simulations were conducted to evaluate the impact of interactions on cumulative infection incidence. Sensitivity analyses were performed to evaluate the robustness of our findings.