Highly-pathogenic avian influenza (HPAI)
Avian influenza A viruses are classified into the following two categories: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI) viruses. The categories refer to molecular characteristics of a bird flu virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting. HPAI viruses are highly contagious among birds and can be deadly to them, especially domestic poultry. Though relatively rare, sporadic human infections with HPAI H5 and HPAI H7 viruses have occurred and caused serious illness and death.