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NIAID > Topics > Flu > Understanding Flu

Understanding Flu

Definitions and Overview

Key Facts About Seasonal Flu

How Flu Spreads

What To Do If You Get Sick

Preventing Seasonal Flu

Seasonal Flu Vaccine

H1N1 Influenza (Swine Flu)

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Community Immunity (Herd Immunity)

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

Featured Study

micrograph of Avian influenza A H5N1

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See Also

Related Links

View a list of links for more information about influenza.

Flu (Influenza)

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Last Updated October 08, 2009

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