The aim of this study is to determine performance characteristics of the FebriDx test in predicting viral or bacterial infection etiology among febrile (observed or reported) patients presenting the emergency department, urgent care centers or primary care offices with suspected acute respiratory tract infection.

This is a prospective, multi-center, observational, blinded clinical trial whereby consented study subjects will be enrolled into two study cohorts: an Acute Respiratory Infection cohort and an Asymptomatic cohort. Subjects (children/adolescents, adults and elderly) with suspected community acquired Acute Respiratory Infection will be enrolled in the Acute Respiratory Infection cohort and subjects without infectious illness will be enrolled in the Asymptomatic cohort. All subjects will undergo FebriDx testing (study device) and results, blinded to subjects and treating physicians, will be compared to a Clinical Reference Algorithm supervised by clinical experts to arbitrate the presence and type of infection (bacterial or viral); the experts are also blinded to the results of FebriDx testing.

The FebriDx® test is a rapid, point-of-care (POC) test that uses a fingerstick blood sample to identify patients with a pathogen induced host immune response through in-vitro detection of both Myxovirus resistance protein A (MxA) and c-reactive protein (CRP) directly from a whole blood sample. MxA is an intracellular protein that becomes elevated in the presence of acute viral infection and CRP is an acute-phase inflammatory protein that is elevated in the presence of a systemic bacterial and/or viral infection.

Acute Respiratory Infection Cohort INCLUSION CRITERIA

• 1 year of age or older
• Exhibit or report of a new onset measured temperature (oral or tympanic) of greater than or equal to 100.5°F/38°C within 3 days (72 hours) of enrollment
• Clinical suspicion for Acute Respiratory Infection and presents with at least one of the following new onset of symptoms: runny nose, nasal congestion, sore throat, cough, hoarse voice or shortness of breath beginning within 7 days before enrollment

Acute Respiratory Infection Cohort EXCLUSION CRITERIA

• Incomplete or invalid testing for comparator method
• Unwilling to participate
• Receiving interferon therapy (e.g. MS, HIV, HBV, HCV) in the last 30 days
• Immunocompromised state (e.g. HIV) or taking immunosuppressive or chemotherapeutic medications in the last 30 days (e.g. oral steroids, Methotrexate, Cyclosporine, Antimetabolite chemotherapy, interferon therapy)
• Taking antibiotics or antiviral therapy in the last 14 days
• Received a live viral immunization in the last 14 days
• Significant trauma or burns (> 5% total body surface area or full thickness (3rd°)) in the last 30 days
• Major surgery (requiring intravenous anesthesia and/or respiratory assistance) in the last 30 days
• Chronic fever without associated respiratory symptoms of greater than 7 days
• History of ear pain plus an exam consistent with otitis media within the last 14 days
• History of a myocardial infarction or stroke in the last 30 days

ASYMPTOMATIC COHORT INCLUSION CRITERIA

• 1 year of age or older
• Absence of infectious signs and symptoms

ASYMPTOMATIC COHORT EXCLUSION CRITERIA

• Fever greater than or equal to 100.5°F /38°C (oral or tympanic) in last 14 days
• Cough
• Chills
• Dyspnea
• Purulent Sputum
• Fatigue
• Pleuritic Pain
• Nasal congestion
• Rhinorrhea (runny nose)
• Sore throat
• Hoarse voice
• Earache
• Autoimmune or rheumatologic disease (e.g. undifferentiated connective tissue disease, Rheumatoid Arthritis, Systemic Lupus Erythematosus (and subsets of Lupus), Sjögren's syndrome, Systemic Sclerosis, Polymyositis and Dermatomyositis, Wegener's granulomatosis)
• Suspected of having any infection
• Receiving interferon therapy (e.g. MS, HIV, HBV, HCV) in last 30 days
• Immunocompromised state (e.g. HIV) or taking immunosuppressive (e.g. oral steroids, Methotrexate, Cyclosporine, Antimetabolite chemotherapy, interferon therapy) in the last 30 days
• Taking antibiotics or antiviral therapy in the last 30 days
• Received a live viral immunization in the last 30 days
• Significant trauma or burns (> 5% total body surface area or full thickness (3rd°)) in the last 30 days
• Major surgery (requiring intravenous anesthesia and/or respiratory assistance) in the last 30 days
• History of a myocardial infarction or stroke in the last 30 days
• Chronic bacterial infection or osteomyelitis
• Known chronic viral infections such as HIV, HCV, HBV, or CMV
• Active tuberculosis
• Acute or chronic (greater than 30 days) diarrhea and/or vomiting
• Urinary tract symptoms in the last 14 days
• Active diarrheal illness within the last 14 days
• Active skin, ocular, or neurologic infections
• Suspected of having otitis media

Patients presenting with a new onset, measured fever (exhibited or reported) and acute respiratory symptoms