Cold versus Flu: Key differences in cause and symptoms

Both are contagious respiratory illnesses caused by different viruses. Flu is caused only by influenza viruses while colds can be caused by rhinoviruses, parainfluenza, or seasonal coronaviruses, and symptoms often overlap so special tests are used to confirm flu.

Influenza (flu) and the common cold are contagious respiratory illnesses caused by different viruses. Flu is caused only by influenza viruses, while the common cold can be caused by several viruses such as rhinoviruses, parainfluenza, and seasonal coronaviruses. Seasonal coronaviruses are distinct from SARS-CoV-2, the virus that causes COVID-19. Because many symptoms are similar, it can be difficult to tell the two apart based on symptoms alone. Key facts: - Flu is caused solely by influenza viruses. - The common cold can arise from multiple viruses, including rhinoviruses, parainfluenza, and seasonal coronaviruses. - Symptoms overlap, but flu symptoms are generally more intense and often begin more abruptly. - Colds are usually milder and commonly include a runny or stuffy nose. - Flu can be associated with more serious complications such as pneumonia, bacterial infections, or hospitalizations. - Special tests can determine whether a person has influenza. Summary: Because symptoms overlap, distinguishing cold from flu by symptoms alone is often not possible, and testing can identify influenza when needed. The key practical difference is that flu can produce more severe illness and has a higher risk of complications, while colds are generally milder.