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Why is testing needed to distinguish influenza from COVID-19 and the common cold?

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Influenza virus — influenza A colored transmission electron micrograph showing influenza viruses (red) at the outer surface of a host cell.

Testing is essential to distinguish between influenza, COVID-19, and the common cold because these conditions are caused by different viruses and often present with overlapping symptoms, such as cough and runny nose.1

While the common cold is typically mild, both influenza and COVID-19 can lead to severe complications like pneumonia and death. Because these diseases require different clinical management and have varying levels of contagiousness and severity, accurate diagnosis is critical for appropriate medical care. For instance, influenza may be treated with specific antiviral drugs, whereas COVID-19 is caused by a distinct virus (SARS-CoV-2) that requires different therapeutic approaches.123

Testing provides the only reliable way to confirm the specific causative agent, ensuring that patients receive the correct treatment and that public health measures can be implemented effectively to prevent further transmission.12