Flu (Influenza)

Understanding Flu

Learn the basics about Flu (Influenza) from causes to complications. NIAID also offers general publications, Spanish language information, and other fact sheets to order or to download and print.

• The Flu Types—Seasonal, Pandemic, Avian (Bird), Swine
• Key Facts About Seasonal Flu
• How Flu Spreads
• Symptoms
• What To Do If You Get Sick
• Preventing Seasonal Flu
• Seasonal Flu Vaccine
• Publications

Ilustrations

Community Immunity Learn how immunizing a critical portion of a community protects most members of the community

How the Flu Virus Changes View illustrations of two ways the flu virus changes: Antigenic Drift Illustration Antigenic Shift Illustration