The frequencies of CD122+NKG2D+ EBV or CMV p/HLA-A*02 tetramer+CD8+ T cells in severe/critical patients were markedly higher than that in the mild/moderate HFRS patients (p EBV<0.01, p CMV <0.01), and were also higher than that in healthy donors (p EBV<0.01, p CMV<0.001, Figure 4B). This evidence concerns the gene KLRK1 and hemorrhagic fever with renal syndrome.