C4A and hemorrhagic fever with renal syndrome: The WBC and neutrophils in peripheral blood, RBC in urine sediments, blood, protein, and glucose in urine, PT/INR, aPTT, TT, AST, ALT, AST/ALT, MAO, AD, urea, creatinine, cystatin C, CK‐MB, LDH, α‐HBDH, mAST, triglycerides, glucose, amylase, ferritin, and PCT in serum increased in HFRS patients along with disease severity, while the lymphocytes, monocytes, platelets, plateletcrit, fibrinogen, serum total protein, albumin, HDL‐c, magnesium, complement C3 and C4, IgG, triiodothyronine, thyroxine, and free triiodothyronine were reduced.