Circulating levels of CD4+ classical and CD4low non-classical monocytes were able to correctly classify individuals developing either DF or DHF with a high degree of accuracy (AUROC 0.8455, p = 0.0075), providing proof of concept for the potential of defined monocyte populations in the blood identified by single cell approaches to predict odds of severe dengue at the onset of fever. The gene discussed is CD4; the disease is dengue disease.