The statistical analyses showed that the frequencies of the epitope-specific CD8+ T cells were much higher in the mild/moderate HFRS patients than that in the severe/critical patients (Mann–Whitney U test, for HLA-A2 restricted epitope: P = 0.007, for HLA-B35 restricted epitope: P = 0.021) (Figure 4A). This evidence concerns the gene CD8A and hemorrhagic fever with renal syndrome.