The evolutionary dynamics of human influenza B virus in Bangladesh, 2007-2025

Abstract

Highlights • Distinct evolutionary trajectories were observed in B/Victoria (B/Vic) and B/Yamagata.• B/Vic diversified rapidly post-2019, whereas B/Yamagata remained conserved and disappeared thereafter.• Hemagglutinin evolved faster than neuraminidase, particularly within the B/Vic lineage.• Purifying selection predominated despite ongoing antigenic drift.