The ts, ca, and att A/Ann Arbor/6/60 H2N2 and B/Ann Arbor/1/1966 have been licensed for human use since 2003 and they have been used as MDV for the generation of both seasonal and potentially pandemic, in the case of IAV, human LAIV by creating reassortant viruses containing the six internal vRNA segments PB2, PB1, PA, NP, M and NS of the IAV or IBV MDV, and the viral glycoprotein-encoding vRNAs HA and NA from viruses that antigenically match the strains predicted to circulate in the upcoming influenza season or potentially pandemic strains. The gene discussed is XK; the disease is influenza.