What is HPAI?
Avian influenza (AI) is broadly divided into highly pathogenic (HPAI) and low pathogenic (LPAI) strains based on its ability to cause disease in poultry. Low pathogenic avian influenza is a natural infection of waterfowl that may cause minimal to no signs of disease in domestic poultry and wild birds.
Highly pathogenic avian influenza rarely causes disease in waterfowl but these birds can transmit it to domestic poultry where it can cause a severe disease with high case mortality (death).
Two types of avian influenza viruses, H5 and H7, are the most common highly pathogenic viruses found in nature. The H5 and H7 avian influenza strains are classified as "Highly Pathogenic Avian Influenza" (HPAI) by the World Organization for Animal Health (OIE) because, to date, HPAI viruses found have always been H5 or H7.
It is important to understand, however, that not all H5 and H7 influenza viruses are highly pathogenic. Likewise, other strains that are not H5 or H7 can be considered highly pathogenic in certain circumstances.