Outbreaks of highly pathogenic avian influenza in Europe: the risks associated with wild birds

The infection of wild birds by highly pathogenic strains of avian influenza (AI) virus was virtually unknown – apart from one instance of the disease appearing in common terns in South Africa in 1961 – before the Asian strain of highly pathogenic AI virus (AIV), H5N1, began to expand across the world. Outbreaks of clinical disease in Eurasia have resulted in visible mortality among populations of free-ranging wild birds in a multitude of species.