Whether the elevated cytokine and chemokine levels cause or contribute to the severity of H7N9 disease has yet to be determined.4 However, the upregulation of pro-inflammatory cytokines and chemokines, such as the monocyte chemoattractant protein-1 (MCP-1/CCL2), IL-6, IL-8, IFN-α, IP-10, MIG and macrophage inflammatory protein-1β was described in H7N9-infected patients with lung injury and severe pneumonia.2 The cytokine levels in C57BL/6 and BALB/c mice infected with H7N9 (A/Anhui/A/2013 strain) were compared. Here, IL6 is linked to pneumonia.