Aberrant production of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interferon-γ (IFN-γ), is frequently observed in the course of lethal infections with influenza virus, and this is thought to be an important factor linked to viral pathogenicity9, 10, 11, 12. This evidence concerns the gene IL6 and infection.