Antithrombin III in Infectious Disease Caused by COVID-19

INCLUSION CRITERIA: 1. \>18y of age, 2. Subject or proxy who can provide informed consent 3. Positive SARS-COV-2 by Polymerase Chain Reaction (PCR) or as determined by clinical team EXCLUSION CRITERIA: 1. Adults or Proxy unable to consent 2. Individuals who are not yet adults (infants, children, teenagers) 3. Pregnant women 4. Prisoners 5. Patients expected to die within 24 hours or with a "do not resuscitate" order, 6. Multi-organ failure, 7. History of hypersensitivity or allergy to any component of the study drug, 8. Ongoing massive surgical or unexplained bleeding, 9. History of bleeding or clotting disorder, 10. Severe traumatic brain injury (Glasgow Coma Scale \<6), 11. Spinal or multiple-trauma, 12. Cancer (incurable/terminal phase) and/or patients receiving palliative care, 13. Enrollment in another concurrent clinical interventional study if considered interfering with this study objectives 14. Per study team discretion, any condition(s) that may prevent safe treatment, preclude adequate evaluation or adding further risk to their underlying illness.