ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Virology
Deceleration and Rebound of Hemagglutinin Divergence in Influenza B/Victoria Across COVID-19 NPI Phases (2016–2024)
Provisionally accepted
- Shandong First Medical University, Tai'an, China
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The COVID-19 pandemic reshaped global viral transmission and created a natural experiment to test how non-pharmaceutical interventions (NPIs) influence the evolution of co-circulating pathogens. We investigated the evolutionary dynamics of the influenza B/Victoria lineage across China, the United States, and Australia—three countries that implemented distinct COVID-19 policy strategies. Using hemagglutinin (HA), neuraminidase (NA), and nucleoprotein (NP) sequences from GISAID (2016–2024), we performed temporal phylogenetic analyses and estimated rate of genetic distance change.Although the duration and strictness of NPIs varied among the three countries, our analysis revealed a transnational common pattern: the evolution of HA showed a marked slowdown during the NPI period. During the post-relaxation period, the population genetic distance of HA in the three countries showed a highly significant increase compared to the pre-pandemic period (comparison between post-relaxation vs. pre-pandemic period, p <0.001).The magnitude and trajectory of these shifts differed by country, broadly aligning with policy timing and intensity. These findings highlight the sensitivity of influenza evolution to population-level interventions and underscore the value of integrating policy metrics into influenza surveillance and pandemic preparedness.
Keywords: COVID-19, hemagglutinin, Influenza Virus, phylogenetics, virus evolution
Received: 20 Jan 2026; Accepted: 11 Feb 2026.
Copyright: © 2026 Zhang, Fu, Yu, Liu, Wang and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Zhao Wang
Kezhou Wang
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