Influenza (flu) is an infection, caused by a virus, that makes you feel very sick, often with fever, headache, body aches, and coughing.
People often use the term "flu" to describe a cold or a stomach virus. But influenza isn't a stomach problem, and it usually feels much worse than a cold.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerChristine Hahn, MD - Epidemiology
Current as ofSeptember 9, 2014
WebMD Medical Reference from Healthwise