CALCA and bacterial infectious disease: In the 59 HFRS patents without secondary bacterial infection (30 patients in mild group and 29 patients in severe group), the median serum PCT level in the severe group patients [1.20 ng/ml (range 0.08–25.00 ng/ml)] was higher than that in the mild group patients [0.79 ng/ml (range 0.05–23.39 ng/ml)] although the difference was not statistically significant (p = 0.085).