HA antigenic variation and phylogenetic analysis of influenza B virus in Shiraz, Iran.

Acta Trop

Department of Bacteriology & Virology, Shiraz Medical School, Shiraz University of medical Sciences, Shiraz, Iran. Electronic address:

Published: September 2024

AI Article Synopsis

  • Influenza B is a contagious respiratory illness with significant health impacts, particularly influenced by the Victoria and Yamagata lineages, leading to vaccine mismatches and increased mortality.
  • A study conducted in Shiraz, Iran from October 2017 to January 2018 tested 235 individuals under 15 with flu-like symptoms, finding a 9.7% positivity rate for influenza B, predominantly manifesting as rhinorrhea and myalgia.
  • Results revealed that the majority of the influenza B viruses belonged to the Yamagata lineage, necessitating enhanced vaccine coverage and continuous monitoring of viral mutations to improve vaccine effectiveness.

Article Abstract

Background: Influenza infection is highly contagious respiratory illness triggered by the influenza virus, bearing substantial implications for global health. Influenza B viruses, specifically the Victoria and Yamagata lineages, have contributed to the disease burden, and the mismatch between circulating strains and vaccine strains has led to increased mortality and economic costs. Understanding the global epidemiology, seasonal variations, and genetic characteristics of influenza B is crucial for effective prevention and control strategies.

Methods: The study investigated influenza B viruses in Shiraz, Iran during the Oct 2017 to Jan 2018. Throat swabs were collected from 235 individuals under 15 with influenza-like symptoms including fever and cough. Samples were stored at -80°C and transported to the lab for further analysis. Viral RNA was extracted and analyzed using Real-time PCR. The hemagglutinin (HA) gene of positive samples was sequenced, and phylogenetic trees were constructed. Amino acids indicative of adaptive mutations were identified using global sequence data.

Results: 23 of 235 samples (9.7 %) were positive for influenza B virus. The most common clinical manifestations were rhinorrhea and myalgia, with 20 individuals (87 % of the 23 infected people) each showing these symptoms. The phylogenetic analysis of the HA gene showed that the Victoria isolates were close to the B/Brisbane/60/2008 strain (12.5 % of the positive samples) and belonged to clade-1A, while the Yamagata isolates were close to the B/Phuket/3037/2013 strain (87.5 % of the positive samples) and belonged to clade-3.

Conclusion: The study highlights the need for importance vaccine coverage in the Shiraz region to address limited genetic diversity and strain mismatch. Continuous surveillance of mutations in the HA gene resulting in amino acid substitutions and their impact on vaccine efficacy is crucial. This study showed that the circulation of influenza B in Shiraz matched with the recommended Yamagata vaccine strain. These findings contribute to the understanding of influenza B dynamics and emphasize the importance of region-specific prevention and control strategies.

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http://dx.doi.org/10.1016/j.actatropica.2024.107292DOI Listing

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