Haemagglutinin is an antigenic glycoprotein which allows viral attachment and entry into the cell. Sixteen subtypes of haemagglutinin (H1-H16) have been described, of which H1, H2 and H3 infect humans. H5 and H7 normally result in avian disease, with some highly pathogenic H5N1 strains causing 100% mortality in poultry. H5N1 has in some cases mutated to infect humans, with 60% mortality. Haemagglutinin H5 is from the Influenza A virus H5N1. Influenza A belongs to the Orthomyxoviridae family, and is a negative sense single-stranded RNA virus which results in respiratory disease. Haemagglutinin is one of the most medically relevant antigens on influenza as it is a target for antiviral drugs and antibodies.
Influenza H5; Influenza NP-A