Avian influenza (or bird flu) is a disease caused by type-A influenza viruses that mainly affects birds. The natural reservoirs (or hosts) of these viruses are wild aquatic birds, such as ducks, geese and swans. The disease can also spread to domestic birds raised for meat, such as chickens and turkeys.

Avian influenza viruses are classified according to two broad categories based on the clinical forms of the disease they can cause – High Pathogenic Avian Influenza (HPAI) and Low Pathogenic Avian Influenza (LPAI).

Find out the main differences between HPAI e LPAI in this video produced by the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), an Italian health authority and research organization in the fields of animal health, food safety and zoonoses and European Union Reference Laboratory (EURL) for Avian Influenza and Newcastle Disease.