We compared the epitope-specific CD8+ T-cell frequencies between patients with mild/moderate HFRS and those with severe/critical HFRS at the earliest available acute stage time point in the 18 patients with HLA-A2 and in the 8 patients with HLA-B35 from whom PBMCs had been collected. The gene discussed is CD8A; the disease is hemorrhagic fever with renal syndrome.