How does the Avian Influenza virus attack organisms like birds?

Avian Influenza virus primarily infects birds, particularly waterfowl, by entering their respiratory and gastrointestinal tracts. The virus attaches to specific receptors on the surface of epithelial cells, allowing it to penetrate these cells and replicate. This replication leads to cell damage and triggers an immune response, which can cause symptoms ranging from mild illness to severe disease. Infected birds can shed the virus in their saliva, nasal secretions, and feces, facilitating its spread to other birds and species.