Influenza viruses are one of the few RNA viruses to undergo replication and transcription in the nucleus of their host cells. Virus replication begins with entry of the virus into the host cell by a process of engulfment called viropexis or receptor-mediated endocytosis. Influenza-A virus HA binds to a Sialic acid receptor on the surface membrane of the infected cell and is then endocytosed. While in the acidic endosome, the HA protein undergoes a conformational change to its low pH form that exposes a hydrophobic fusion peptide. Following internalization, the calthrin coat is removed and vesicles fuse with the endosomes. The virus is exposed to the cytoplasm and the vRNPs (viral Ribonucleoprotein Complex) are released and then transported into the nucleus (Ref.3). In the nucleus, the vRNPs serve as templates for the production of two forms of positive-sense RNA: viral mRNA (messenger RNA) and cRNA (complementary RNA). The synthesis of mRNA is catalyzed by the viral RNA-dependent RNA polymerase (comprising the three subunits PA, PB1 and PB2), which is part of the incoming vRNP complex. Viral mRNAs are processed in an analogous fashion to other eukaryotic mRNAs; that is, they are capped (i.e. contain a methylated 5 guanosine residue) and are polyadenylated (i.e. contain a sequence of polyadenylic acid at their 3 end), and exported from the nucleus for translation by cytoplasmic ribosomes. The nuclear export of viral mRNA utilizes the ‘machinery’ of the host cell, but is selective; export is controlled by the viral non-structural protein NS1 (Ref.4). Many viral proteins (NP, M1, NS2 and the polymerases) are then imported into the nucleus for the final stages of replication and for vRNP assembly. The viral cRNA is neither capped nor polyadenylated, but, instead, is a perfect copy of the template. These cRNAs then form the template for synthesis of further negative-sense genomic vRNA segments for amplification of mRNA synthesis and packaging into progeny virions. Both cRNA and vRNA molecules contain a 5’ triphosphate group. Progeny virions are assembled at the apical surface of the plasma membrane and, therefore, newly synthesized RNPs must be exported from the nucleus and directed to the plasma membrane to allow their incorporation into budding virions