The Sofia 2 Flu + SARS Antigen FIA employs immunofluorescence technology in a sandwich design that is used with Sofia 2 to independently detect and differentiate nucleocapsid protein from SARS-CoV-2, influenza A and influenza B. Symptoms of respiratory viral infection due to SARS-CoV-2 and influenza can be similar. Sofia 2 Flu + SARS Antigen FIA is intended for the qualitative detection of the nucleocapsid protein antigens in direct nasopharyngeal (NP) and nasal (NS) swab specimens from individuals who are suspected of COVID-19 by their healthcare provider within the first five days of the onset of symptoms, and/or for use as an aid in the rapid differential diagnosis of acute influenza A and influenza B viral infections. The test detects, but does not differentiate, between SARS-CoV and SARS-CoV-2 viruses and is not intended to detect influenza C antigens. Testing is limited to laboratories certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA), 42 U.S.C. §263a, to perform moderate complexity/high complexity tests. The Sofia 2 Flu + SARS Antigen FIA is also authorized to be distributed and used in patient care settings outside of the clinical laboratory environment.