An avian influenza A-H5N1 virus (clade 2.3.4.4b) has infected and killed hundreds of millions of wild and domesticated birds, thousands of wild mammals and farmed fur animals, and some pets (1), exhibiting the characteristics of a panzootic disease (2). H5N1 has recently spilled over into cattle in the US, refuting theories that cattle were not susceptible to infection by influenza A viruses (3). As of 15 October, the H5N1 strain of avian influenza has been found in 300 cattle farms in 14 US states (4). The virus has also infected 20 human beings (5). US guidelines for managing H5N1 infections differ widely between poultry and cattle. To ensure the reduction of spillover risk of a zoonotic virus with pandemic potential, jurisdictions with infected animals should adopt effective, ethical policies and apply them consistently to all farmed species.
