Evaluating a Host-response Based Diagnostic for Distinguishing Between Bacterial and Viral Etiology in Patients With Lower Respiratory Tract Infection (LRTI)

Inclusion Criteria: * Patients aged 18 years and older who agree (or their legal guardian agree) to sign an informed consent will be eligible for inclusion. * The LRTI cohorts should also fulfill the following criteria: * Peak measured (not tactile, self-reported acceptable) temperature ≥ 37.8°C (100°F) within the last 7 days (AND) * Symptoms duration ≤7 days (AND) * Clinical suspicion of LRTI or pneumonia Exclusion Criteria: * Oral/intravenous/intramuscular antibiotic treatment of over 48/12/12 hours' duration at time of enrollment (respectively), unless temperature ≥ 37.8°C was measured within the last 2 days * Another episode of an acute infection during the last 2 weeks * Congenital immune deficiency (CID) * A proven or suspected human immunodeficiency virus (HIV)-1, hepatitis B virus (HBV), or hepatitis C virus (HCV) infection * Active malignancy * Pregnancy * Current treatment with immune-suppressive or immune-modulating therapies including without limitations: * Use of high dose steroids \>1 mg/kg/day prednisone or equivalent in the past two weeks * Monoclonal antibodies * Intravenous immunoglobulin (IVIG) * Cyclosporine, Cyclophosphamide, Tacrolimus * Granulocyte/Monocyte colony stimulating factor (G/GM-CSF) * Anti-Tumor Necrosis Factor (TNF) agents * Interferon (of all kinds) * Other severe illnesses that affect life expectancy and quality of life such as: * Moderate to severe psychomotor retardation * Post-transplant patients (including solid organs, allogeneic/autologous stem cell transplantation) * Moderate to severe congenital metabolic disorder