We previously demonstrated that TNF-α was hyper-induced in autopsy lung tissue from patients with H5N1 disease [9] and in H5N1-infected human macrophages in vitro as early as 3 h post-infection [14] and have suggested that increased production of pro-inflammatory cytokines in response to H5N1 compared to H1N1 infection may be an important factor contributing to H5N1 pathogenesis. Here, TNF is linked to infection.