The viral genome of IAV consists of eight single-stranded negative sense RNA segments that encode at least 11 viral proteins, including two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA) [6] . Based on the antigenic properties of HA and NA, IAVs have been classified into 16 HA subtypes and 9 NA subtypes [7] . All 16 HA subtypes have been identified in avian species, while only 6 HA subtypes (H1, H2, H3, H5, H7 and H9) are known to infect human beings [8, 9, 10] . H1, H2 and H3 subtypes have caused pandemics, while H1 and H3 also dominate seasonal epidemics together with influenza B virus.