Avian influenza, also known as bird flu, has been devastating poultry farms in major countries over the past four years, causing a significant decline in global wild bird populations. The virus has also affected mammals and humans.
Researchers Marcel Klaassen and Michelle Wille found that farm birds, mainly hens, chickens, geese, and ducks, are heavily affected due to their large population share (70% of world birds) and collective culling measures after the first infection case.
A recent study published in Nature Ecology & Evolution reveals that a new viral offshoot emerged in 2021 within the H5N1 avian influenza family. Variants of this clade, specifically 2.3.4.4b, have spread globally, infecting wild birds across multiple continents. Initially affecting Asia and Europe, the outbreak later expanded to North America, South America, and even remote areas without poultry.
The adaptation of the virus from poultry to wild birds explains the sudden increase in sustainable outbreaks among wild birds. This shift has significant implications for global health and wildlife conservation efforts.
Source: https://www.lemonde.fr/en/environment/article/2025/04/11/bird-flu-how-the-virus-has-conquered-the-planet-thanks-to-bird-migration_6740120_114.html