The particular order of infections that we focused on results from our observations that (i) RSV induces higher levels of IFN-β production than IAV, (ii) IFN-β-stimulated cells are more resistant to infection with IAV than to infection with RSV, and (iii) IAV is sensitive to IFN-λ, and this sensitivity does not rely solely on STAT1/2 signaling. This evidence concerns the gene IFNB1 and infection.