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The external H
and N envelope glycoproteins carry the subtype antigens H1 to H15 and N1 to N9. Vaccinal
immunity involves neutralisation of the subtype specific antigens on H. H1 to H15 viruses are in ducks which are the source of new mammalian subtypes (see later). Equine influenza type 1 and type 2 carry H7 N7 and H3 N8 respectively ie their vaccines do not cross protect. |