IJID regions · 2026
The evolutionary dynamics of human influenza B virus in Bangladesh, 2007-2025.
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Islam Suprova, Hasan Mehedi
Аннотация
OBJECTIVES: Influenza B virus causes significant seasonal respiratory illness, yet its long-term evolutionary data from South Asia remain limited. We investigated the evolutionary dynamics of influenza B viruses circulating in Bangladesh during 2007-2025.
METHODS: Complete hemagglutinin (HA) and neuraminidase (NA) gene sequences were analyzed using phylogenetic, evolutionary, demographic, selection pressure, amino acid variation, glycosylation, and genetic proximity analyses.
RESULTS: Phylogenetic analyses showed clear segregation into the B/Victoria (B/Vic) and B/Yamagata (B/Yam) lineages. B/Vic viruses diversified after 2019 into multiple V1A-derived subclades, whereas B/Yam remained genetically conserved before disappearing after 2019. Viruses maintained high similarity to season-matched vaccine strains. HA evolved faster than NA (2.48 × 10-3 vs 2.12 × 10-3 substitutions/site/year), with the highest rate observed in B/Vic HA. Viral effective population size expanded during 2014-2016 and 2017-2019, followed by a marked decline during 2019-2021. Purifying selection predominated, although episodic diversifying selection occurred mainly in B/Vic viruses. Amino acid diversification was concentrated within HA antigenic loop regions, while glycosylation profiles remained largely conserved.
CONCLUSION: B/Vic viruses in Bangladesh exhibited substantially greater evolutionary flexibility than B/Yam, driven primarily by antigenic diversification of HA. Continued genomic surveillance is important for monitoring viral evolution and informing vaccine strain selection.
METHODS: Complete hemagglutinin (HA) and neuraminidase (NA) gene sequences were analyzed using phylogenetic, evolutionary, demographic, selection pressure, amino acid variation, glycosylation, and genetic proximity analyses.
RESULTS: Phylogenetic analyses showed clear segregation into the B/Victoria (B/Vic) and B/Yamagata (B/Yam) lineages. B/Vic viruses diversified after 2019 into multiple V1A-derived subclades, whereas B/Yam remained genetically conserved before disappearing after 2019. Viruses maintained high similarity to season-matched vaccine strains. HA evolved faster than NA (2.48 × 10-3 vs 2.12 × 10-3 substitutions/site/year), with the highest rate observed in B/Vic HA. Viral effective population size expanded during 2014-2016 and 2017-2019, followed by a marked decline during 2019-2021. Purifying selection predominated, although episodic diversifying selection occurred mainly in B/Vic viruses. Amino acid diversification was concentrated within HA antigenic loop regions, while glycosylation profiles remained largely conserved.
CONCLUSION: B/Vic viruses in Bangladesh exhibited substantially greater evolutionary flexibility than B/Yam, driven primarily by antigenic diversification of HA. Continued genomic surveillance is important for monitoring viral evolution and informing vaccine strain selection.