CD4 and dengue disease: First, we aimed to understand if there were any differences in the frequencies of Tregs (CD4+CD25+FOXP3+) and activated T cells (Tacts: CD4+CD25+FOXP3−) in the blood of patients with acute dengue infection (<4 days after onset of fever; see Table 1) compared to HDs or in patients undergoing classical DF compared to more severe DHF/DSS patients (Fig. S1).