The flu, or influenza, is caused by influenza viruses. There are several types of influenza viruses, including types A, B, and C, but it is primarily caused by influenza types A and B.
Influenza, commonly known as the flu, is caused by the influenza virus. There are different types of influenza viruses, including influenza A, B, and C. Influenza A and B viruses are responsible for seasonal flu outbreaks each year.