Multivariate analysis for the entire cohort revealed that PCT, WBC and hemorrhage were independent factors associated with the severity of HFRS (OR 2.544, 95% CI 1.330–4.868, p = 0.005; OR 1.082, 95% CI 1.014–1.155, p = 0.017 and OR 2.149, 95% CI 1.004–4.599, p = 0.049; respectively, Table 2). This evidence concerns the gene CALCA and hemorrhage.