IL2 and hemorrhagic fever with renal syndrome: HTNV-Gn/Gc peptides elicited substantially higher frequencies of single IFN-γ (median 0.746% of total CD4+T cells), IL-2 (median 0.172% of total CD4+T cells) and TNF-α (median 0.868% of total CD4+T cells) or dual-cytokine (median 0.209% for IFN-γ+IL-2+CD4+T cells and median 1.100% for IFN-γ+TNF-α+CD4+T cells) secretion from specific CD4+T cells in mild/ moderate HFRS patients.