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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. For more information, see Key Facts about Seasonal Flu Vaccine.

Key Facts About Seasonal Flu

A summary of key seasonal flu facts and who should get vaccinated...

2013-2014 Flu Season

Information about the 2013-2014 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...

Regular Flu Season

General information on regular flu seasons in the United States...

Seasonal Flu and Staph Infections

Information about flu and staph infections, MRSA...

Questions & Answers


 Health Insurance Marketplace. Marketplace plans cover free flu vaccines.

The Flu I.Q. widget is an interactive quiz to test your flu knowledge.
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