The detection of high levels of circulating IL-15 is of interest, since this cytokine has been shown to be a major stimulator of NK cells [36] and T cells [37] . Thus our data suggest that these lymphocytes population might be activated during acute infection and may also contribute to viral control during the acute phase of CHIKV infection. Detection of soluble IL-2R in the plasma suggests T cell activation since this molecule is secreted by activated T cells [38] . Experiments are planned to study the activation phenotype of T and NK cell subsets in acutely infected patients.