Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Severe COVID-19 Disease Male or female participants ≥ 18 years of age. 2. Participants with SARS-CoV-2 infection, as defined by standard reverse transcriptase polymerase chain reaction (RT-PCR) assay or equivalent test. 3. Must have pulmonary infiltrate on radiologic examination. 4. Participant must have a clinical diagnosis of high-risk ARDS (as defined by a PaO2-to-FiO2 ratio of < 150 mm Hg) requiring intensive respiratory support, including non-invasive methods such as high-flow nasal cannula or mechanical ventilation. 5. AST and ALT ≤ 3 x upper limit of normal (ULN). 6. Consent must be given before performance of any study related procedure not part of standard medical care, with the understanding that consent may be withdrawn at any time without prejudice to future medical care. Informed consent can be obtained from healthcare proxy if the participant is unable to provide consent due to medical status  Active uncontrolled infection with a non-COVID-19 agent. 2. Diagnosis of ARDS that is not considered to be high-risk, as defined by PaO2-to-FiO2 ratio of ≥ 150 mm Hg. 3. Any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. End-stage liver disease with ascites unrelated to COVID-19 (Childs Pugh score > 12). 5. Uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with New York Heart Association functional classification III or IV, myocarditis, pericarditis, or significant pericardial effusion. 6. Known chronic kidney disease of Stage 4 or 5 severity or requiring hemodialysis. 7. COVID-19-associated acute kidney injury requiring dialysis. 8. HIV, hepatitis B, or hepatitis C seropositive. 9. Patients with baseline QTc interval prolongation, as defined by repeated demonstration of a QTc interval >500 milliseconds. 10. Patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. Pregnant or breastfeeding participants. 12. Patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. Effective forms of birth control, which must be continued through the entire on-study 6-month interval, Abstinence; Intrauterine device (IUD); Hormonal (birth control pills, injections, or implants); Tubal ligation; or Vasectomy. 13. Participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. Recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. History of WHO Class III or IV pulmonary hypertension. 16. Severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. Participants may be excluded at the discretion of the PI or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk