Influenza (flu) and COVID-19 are both contagious respiratory illnesses, but they are caused by different viruses. COVID-19 is caused by infection with a new coronavirus and flu is caused by infection with influenza viruses.

There are some key differences between flu and COVID-19:

  • COVID-19 seems to spread more easily than flu and causes more serious illnesses in some people. It can also take longer before people show symptoms and people can be contagious for longer.
  • Another important difference is there are multiple FDA-licensed influenza vaccines produced annually to protect against the flu. Currently, we have two (many under development) COVID-19 vaccines that have been approved by the U.S. Food and Drug Administration for emergency use authorization.

Because some of the symptoms of flu and COVID-19 are similar, it may be hard to tell the difference between them based on symptoms alone, and testing may be needed to help confirm a diagnosis.

Source:
CDC: Similarities and Differences between Flu and COVID-19​