Influenza A viruses (IAVs)maintained among wild waterfowl, gulls, shorebirds, and some seabirds, and typically do not cause disease. Some avian-origin IAVs that have previously spilled over into domestic poultry have developed a highly pathogenic phenotype and have become important pathogens affecting both wild birds and poultry. These avian-origin IAVs have important implications to the production and trade of domestic birds, conservation and management of wild birds, and the risk of spillover of zoonotic influenza to humans handling infected birds.