ns unknown [15]. Among all known influenza viruses, only IAVs are subtyped according to their HAs (H) and neuraminidase (NA or N) spikes into H1–H18 and N1–N11. Several subtypes of IAVs, including H1N1, H3N2 and H5N1, have crossed the species barrier to infect a variety of birds and mammals including humans, indicating that they have zoonotic potential. IAVs not only mutate quickly but also prefer to reassort with other IAVs to form a new strain. Due to these properties, I