Influenza surveillance and analysis of the HA gene characteristics of Influenza A H1N1 virus in Dalian City from 2015 to 2018

Abstract

Background:
Influenza A H1N1 virus remains a major cause of seasonal influenza outbreaks worldwide. The hemagglutinin (HA) gene plays a key role in viral infectivity and antigenicity, and its genetic variation influences vaccine effectiveness and viral evolution.
Objective:
To conduct influenza surveillance and analyze the molecular characteristics of the HA gene of Influenza A H1N1 viruses circulating in Dalian City from 2015 to 2018.
Methods:
Respiratory specimens were collected from patients with influenza-like illness in sentinel hospitals in Dalian between 2015 and 2018. Virus isolation and subtyping were performed using RT-PCR. The HA gene was sequenced from representative H1N1 strains. Phylogenetic analysis and mutation identification were conducted to assess genetic variation and evolution.
Results:
A total of [XXX] Influenza A H1N1 positive samples were identified. Phylogenetic analysis showed that circulating strains belonged predominantly to clade [X], with several amino acid substitutions in antigenic sites of the HA protein. Key mutations included [list mutations], which may affect viral binding affinity and antigenicity. Seasonal variation in strain predominance was observed.
Conclusion:
Continuous surveillance of the HA gene provides critical information on the genetic evolution of Influenza A H1N1 virus in Dalian. Monitoring these changes is essential for updating vaccine strains and improving influenza prevention strategies.
Keywords:
Influenza A H1N1, HA gene, molecular characterization, phylogenetics, surveillance, Dalian City