•Neutropenia and lymphocytosis [64] low leukocytes but increased lymphocyte numbers [69]•Strain mismatched antibodies can promote infection of monocytes [64]•T cells are protective but strain mismatched T cells may [72] contribute to cytokine overload•Denv infected monocytes and mast cells promote vascular leakage [68, 73]•described as a ‘cytokine tsunami’ [74, 75] with high levels of TNFa and IL6 [76, 77] causing capillary leak and pleural effusion [78–80]•MCP1 [49], VEGF and loss of plasma VEGFR2 [81, 82]•IFN signaling key to blocking DENV replication [66]•Elevated kynurenine [83]. The gene discussed is CCL2; the disease is neutropenia.