Seasonal Influenza: Flu Basics

Influenza (the flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to 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 three 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 an influenza B virus.

Key Facts About Seasonal Flu

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

2012-2013 Flu Season

Information about the 2012-2013 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 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

• Seasonal Influenza
• Cold Versus Flu
• Seasonal Flu & Staph Infection
• Seasonal Flu & Other Respiratory Viruses
• Seasonal Influenza-Associated Hospitalizations in the United States
• Estimating Seasonal Influenza-Associated Deaths in the United States
• Misconceptions about Seasonal Influenza and Influenza Vaccines