Elevated serum levels of pro-inflammatory mediators (‘cytokine storm’) [345,346,347]—suspected to contribute to vascular permeability—increased expression of the early activation marker CD69 on CD8+ T cells [348], and higher frequencies of circulating DENV-specific CD8+ T cells [323] in patients with DHF than in those with DF initially supported a link between the T-cell response and disease severity. The gene discussed is CD8A; the disease is dengue disease.