Evaluate the Efficacy and Safety of Various Treatment Schemes for Severe Fever With Thrombocytopenia Syndrome(SFTS)

Inclusion Criteria: 1. Age ≥18 years. 2. SFTS Patients met the following diagnostic criteria:SFTS-virus (SFTSV) positive in peripheral blood detected by RT-PCR or Next Generation Sequencing (NGS) . 3. The intervention group shall meet the following conditions: Part A: Treatment can be initiated if the patient has two of the following conditions: (1) Persistent high fever for 7 days or more; (2) Platelets less than 50×10^9/L; (3) Multiple organ function impairment (MODS) including brain, heart, liver, kidney and blood coagulation; (4) Failure of more than 1 organ, such as brain, heart, liver, kidney and coagulation. Part B: Serum cytokine IL-6 quantification >2 times the upper limit of normal (ULN). Part C: Plasma D-D dimer ≥ 4×ULN. 4. Sign written informed consent and cooperate with follow-up. Exclusion Criteria: Patients with neoplastic diseases. Patients with severe chronic diseases, such as chronic kidney disease stage 3-5, chronic heart failure, decompensated cirrhosis, chronic diseases of the central nervous system, hematologic neoplastic diseases, uncontrolled solid tumors, etc. Patients who are or may be pregnant. Patients with a history of hypersensitivity reaction to the trial drug and its components. Patients with conditions that the investigator judged to affect short-term survival. Additional exclusion criteria for Part B: Patients with platelet < 50×10^9/L Additional exclusion criteria for Part C: Received vasopressor therapy for more than 36 hours before enrollment; Indications for anticoagulant therapy (such as ACS, acute VTE, mechanical valve, etc.); Significant bleeding risk as evidenced by one of the following conditions: Clinical: Surgery that requires general or spinal anesthesia within 24 hours prior to enrollment, or may require such surgery within the next 24 hours; Evidence of active bleeding; A history of severe head trauma requiring hospitalization; History of intracranial surgery or stroke or any cerebral arteriovenous malformation, cerebral aneurysm, or central nervous system mass within 3 months prior to the study; History of congenital hemorrhage; Gastrointestinal bleeding occurred within 6 weeks before the study unless corrective surgery was performed; Trauma that is thought to increase the risk of bleeding; The presence of an epidural catheter; Laboratory: INR > 2.0, or thrombelastogram results suggest significant hyperfibrinolysis. Present with other forms of shock that are clinically apparent, including cardiogenic, obstructive (massive pulmonary embolism, cardiac tamponade, tension pneumothorax), hemorrhagic, neurogenic, or anaphylactic shock.