Avian influenza viruses have infected the world’s birds for millennia. We first became aware of them in the 19th century, when mass deaths of poultry triggered interest in what was then called “fowl plague”.
But in 2021, something fundamental changed. As the world grappled with COVID lockdowns and economic chaos, the birds of the world were encountering a new strain, known formally as Highly Pathogenic Avian Influenza (HPAI) H5N1 2.3.4.4.b. It spread easily and was capable of causing disease and death in a far wider number of bird species than previously seen before.
