Cardiomyocyte-specific attenuation of the virus via miR targeting revealed an important role for the direct infection of cardiomyocytes in influenza-associated cardiac inflammation, as manifested in IFITM3 KO mice by (i) a roughly 1- to 1.5-log decrease in mean cardiac viral titers, (ii) markedly reduced levels of inflammatory cytokines IFNβ and IL-6 (Fig. 4, B and C), and (iii) attenuated CD45-positive immune cell infiltration (Fig. 4, D and E). This evidence concerns the gene IFNB1 and influenza.