Levels of pulmonary neutrophils and their associated chemokines, such as interleukin-8 (IL-8), are correlated with clinical symptom severity of influenza infection in humans [12–14], and aberrant immune response has been implicated in fatal cases of influenza [15, 16], suggesting a correlation between disease severity and the CXC chemokine receptor 2 (CXCR2)-IL-8 axis. This evidence concerns the gene CXCR2 and influenza.