Similar to airway epithelial cells, human macrophages express type I and type III IFNs, IL-1α, IL-1β, IL-6, TNF-α, CXCL8, CCL2 (MCP-1), CCL3 (MIP-1α), CCL4 (MIP1-β), CXCL9, and CXCL10 following infection with seasonal H1N1 or with H5N1, 2009 H1N1 strains demonstrating increased pathogenicity (Geiler et al., 2011). Here, CCL3 is linked to infection.