What makes influenza a respiratory virus?

[Yelnif]

Actually, it's not the proteins involved in viral entry into cells that
makes inflenza virus a respiratory virus.  Infact, many if not all cell
types are infected with influenza because the virus recognizes sialic acid
residues which are present on many cell membrane proteins.  What makes the
virus a respiratory virus is the fact that only infected lung cells are
capable of producing a successful infection.
-Finley
jfinley at orion.cmc.uab.edu