Seasonal Influenza: Flu Basics
Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness. Serious outcomes of flu infection can result in hospitalization or death. Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications. The best way to prevent the flu is by getting vaccinated each year.
The upcoming season's flu vaccine will protect against the influenza viruses that research indicates will be most common during the season. This includes an influenza A (H1N1) virus, an influenza A (H3N2) virus, and one or two influenza B viruses, depending on the flu vaccine.
- Key Facts About Seasonal Flu
A summary of key seasonal flu facts.
- 2015-2016 Flu Season
Information about the 2015-2016 flu season.
- Symptoms & Complications
Flu symptoms and complications.
- People at High Risk from Flu
Some people are more likely to get flu complications that result in being hospitalized and occasionally result in death.
- How Flu Spreads
How the virus spreads and how long people may be contagious.
- Past Flu Seasons
Information about past flu seasons.
- Disease Burden of Influenza
- New! Glossary of Influenza (Flu) Terms
A glossary of flu terminology and associated definitions used by CDC
Related Questions & Answers
- Seasonal Influenza
- What You Should Know for the 2015-2016 Influenza Season
- Misconceptions about Seasonal Flu and Flu Vaccines
- Cold Versus Flu
- Seasonal Flu & Other Respiratory Viruses
- Seasonal Influenza-Associated Hospitalizations in the United States
- Estimating Seasonal Influenza-Associated Deaths in the United States
- FAQ: The Flu Season
- Page last reviewed: August 15, 2014
- Page last updated: May 4, 2016
- Content source:
- Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)
- Page maintained by: Office of the Associate Director for Communication, Digital Media Branch, Division of Public Affairs