H5N9 so confusing I thought bird flu was H1N1, but apparently not. Influenza A viruses (IAVs) are divided into subtypes based on the antigenicity of their mem

H5N9 so confusing I thought bird flu was H1N1, but apparently not. Influenza A viruses (IAVs) are divided into subtypes based on the antigenicity of their membrane-bound surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). Sixteen distinct HA subtypes (H1-H16) and 9 NA subtypes (N1-N9) have been identified that circulate in wild bird populations IAVs are further divided into highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI), which refers to their ability to cause disease in domestic poultry poultry in this case = a duck Quack quack