How do you know I have flu (influenza) and not COVID-19? (For patients that are influenza positive, COVID-19 negative)

The test detected the presence of influenza in your sample. This means you were positive for the influenza at the time of testing. The SARS-CoV-2 (COVID-19) virus was not detected in your sample. This means you were negative for SARS-CoV-2 (COVID-19) at the time of testing.