We and others have shown that expression of granulocyte macrophage-colony stimulating factor (GM-CSF) in the lung provides remarkable protection against seasonal influenza (H3N2), PR8 (H1N1), pandemic flu (H1N1) and secondary bacterial pneumonia due to Staphylococcus aureus after influenza infection [2–6]. The gene discussed is CSF2; the disease is bacterial pneumonia.