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In 2024, influenza A(H5N1) genotype B3.13 viruses emerged from cattle and caused mild spillover infections in humans. Using human bronchus and lung tissue, we evaluated tropism, replication, and pathogenesis of 2 cattle influenza isolates.
Those viruses showed moderate replication competence and induced robust proinflammatory responses, suggesting potential risk for human health. Highly pathogenic avian influenza (HPAI) H5N1 viruses remain a major global health concern, particularly because of sporadic spillover into mammals ( 1 ).
HPAI A(H5N1) clade 2.3.4.4b viruses entered the United States through a trans-Atlantic introduction in late 2021, after which extensive reassortment among migratory birds produced the B3.13 and D1.1 genotypes. Those variants have spread widely, driving outbreaks in livestock and causing occasional human infections ( 2 , 3 ).
CDC Emerging Infectious Diseases Journal published a clinical update in Infectious Disease on 01 Apr 2026.
The item focuses on Tropism and Replication Competence of Cattle Influenza A(H5N1) Genotype B3.13 Virus in Human Bronchus and Lung Tissue.
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