Dominant HA motif 131/132-NT shapes the phenotype of avian H9N2 influenza virus by modulating agglutination property, receptor specificity and infectivity in animals

Description

Xue Chen and colleagues report in 2026 on a puzzling change in the H9N2 bird flu virus, which lives in poultry and can spill over into people. Since 2021, the virus has largely lost its ability to clump chicken red blood cells, a property that routine flu testing depends on. The team traces that loss to two changed building blocks in the virus surface protein called hemagglutinin.

Working from virus records, lab assays, and animal tests, the group shows that cells from turkeys or guinea pigs restore detection where chicken cells fail. The changed protein also binds more weakly to one kind of sugar receptor on cell surfaces. In mice the altered virus grew less in the lungs, while chickens stayed strongly infected. The authors urge testing labs to add other cell types so spreading viruses are not missed.

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Source: https://europepmc.org/article/MED/PMC13469311