Analysis of NS1, which may also contribute to the virulence of influenza (H5N1), showed a deletion of 5 amino acids that is similar to that found in genotype-Z influenza (H5N1) viruses and that may contribute to increased expression of tumor necrosis factor-α and interferon-γ–inducible protein 10 (IP-10) in primary human macrophages (2). This evidence concerns the gene TNF and influenza.