Looking 7 days post-infection with WNV-E218A we observed that in whole brain samples, macrophages, but not other infiltrating leukocyte populations exhibited higher proportions of cell death as quantified by the viability dye ZombieNIR (Fig 6A). To elucidate the extent of this phenotype we also analyzed Il33–/–mice and congenic controls at 14 DPI with WNV-E218A, and again found that only brain macrophage populations showed enhanced ZombieNIR positivity (S6A Fig). This evidence concerns the gene IL33 and infection.