Inclusion Criteria:  ≥ 18 years old The first vital sign (any one of: blood pressure, temperature, pulse or respiratory rate) has been recorded in the medical record A 300µl blood sample originally collected in a K2 EDTA (hematology purple top) tube within 4 hours of the first recorded vital sign is available. Sign or suspicion of infection, defined as meeting either of criterion A-1 and A-2 (based on temperature, WBC, heart rate, respiratory rate and/or culture order criteria):  Exclusion Criteria:  Patients in whom a palliative care or hospice course is expected during ED visit Self-reported, documented or otherwise known to be actively enrolled on any experimental/investigational therapeutic medication prior to blood collection Self-reported, documented, or known history of a hematologic malignancy (any leukemia, lymphoma, or myeloma), myelodysplastic syndrome, or myeloproliferative disorder Self-reported, documented or otherwise known to receive a chemotherapeutic agent or other excluded medication in the past 3 months (Appendix C) Self-reported, documented or otherwise known to have undergone a hematopoietic stem cell transplant or any solid organ transplant Patients transferred to the Emergency Department from another acute care facility Residents or patients of a hospital-based skilled nursing facility