What Is the Flu?
By Ingrid StrauchMedically Reviewed by Robert Jasmer, MD
Influenza, a viral infection, causes an illness that can range from mild to life-threatening.
Influenza, commonly known as "the flu," is a viral infection of the respiratory tract that affects the nose, throat, and sometimes lungs.
Outbreaks of flu tend to happen annually, at about the same time every year. This period is commonly referred to as "cold and flu season."
https://www.everydayhealth.com/flu/guide/
