University of Kansas Medical Center

Patients eligible for inclusion are required to fulfill all of the following criteria: - Written informed consent must be obtained from the patient or his/her legal guardian. - 18 years of age or older. - Current disease duration ≤ 7 days. - Tactile fever or measured temperature ≥ 37.8°C (100°F) (any body site, any measurement device, including self-reported), either of them noted at least once within the last 7 days. - Clinical suspicion of bacterial or viral LRTI: At least one of the following respiratory signs or symptoms: cough (new or worsening), sputum production, dyspnea/shortness of breath, auscultatory abnormality (e.g. wheezing, rhonchi). - Clinician intent to prescribe antibiotics based on the currently available data.

Patients fulfilling any of the following criteria are not eligible for inclusion in the infectious cohort: - Systemic antibiotics within 72 hours prior to enrollment - Inflammatory disease (e.g., IBD, SLE, Rheumatoid arthritis, Kawasaki, other vasculitis) - Congenital immune deficiency (CID) - A proven or suspected infection on presentation with Mycobacterial (e.g., MAC, MABC), parasitic or fungal (e.g., Candida, Histoplasma, Aspergillus) pathogen - HIV, HBV, or HCV infection (self-declared or known from medical records) - Major surgery, trauma and\or burns in the last 7 days - Pregnancy- self reported or medically confirmed - Active malignancy - Cancer diagnosed within the previous six months, recurrent, regionally advanced or metastatic cancer, cancer for which treatment had been administered within six months, or hematological cancer that is not in complete remission. - Patients with severe illnesses that affect life expectancy and quality of life such as end stage renal disease, end stage liver disease or severe COPD. - Clinician intent to hospitalize patient. - Patients with suspected concomitant infections (e.g. UTI, cellulitis, gastroenteritis, etc.) - Active treatment with immune-suppressive or immune-modulating therapies, including without limitations: - Administration of PO\IV\IM high dose steroids >1mg/kg/day Prednisone (or equivalent) at some point in the past 10 days or daily continuous use of steroids > 0.25 mg/kg/day in the past 7 days - Monoclonal antibodies, anti-TNF agents - Intravenous immunoglobulin (IVIG) - Cyclosporine, Cyclophosphamide, Tacrolimus, Azathioprine, Methotrexate - G/GM-CSF, Interferons - Considered unsuitable for the study by the study team