Recombinant equine influenza viruses were recovered after transfection of MDCK (Madin Darby Canine Kidney) cells with DNA plasmids coding for each of the eight influenza RNAs (HA, M, NA, NS, PA, PB1 and PB2) simultaneously with plasmids expressing the proteins PA, PB1, PB2, NP and NS1 [117]. Here, XK is linked to influenza.