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 and who should get vaccinated.
- 2014-2015 Flu Season
Information about the 2014-2015 flu season.
- Past Flu Seasons
Information about past flu seasons.
- Symptoms & Severity
Flu symptoms and how some people are at greater risk from severe 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.
- The Flu Season
General information on regular flu seasons in the United States.
- 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 2014-2015 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: July 23, 2015
- Content source: