Skip Navigation

Turn on more accessible mode

Turn off more accessible mode

Skip Ribbon Commands

Skip to main content

Department of Health and Human Services • National Institutes of Health

Advanced Search

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)

Skip Website Tools

Website Tools

Skip Stay Connected

Stay Connected

Stay connected on Facebook

Stay connected on Twitter

Stay connected on flickr

Stay connected on YouTube

Stay connected on LinkedIn

Social media privacy policy and disclaimers.

Flu.gov

Community Immunity (Herd Immunity)

Link to Community Immunity (Herd Immunity) illustration
Learn how immunizing a critical portion of a community protects most members of the community.

Featured Study

micrograph of Avian influenza A H5N1

Join the fight against influenza! Volunteer for NIAID clinical studies.

See Also

Related Links

View a list of links for more information about influenza.

CDC, in coordination with its Advisory Committee for Immunization Practices, has additional recommendations for influenza vaccine use.

Flu (Influenza)

JavaScript is disabled in your browser. To view this content, please enable JavaScript and refresh the page.Click here for instructions on how to enable JavaScript in your browser.

Last Updated September 24, 2008

Home | Contact Us | Help | Site Map | Accessibility | Privacy Policy | Disclaimer | Web Site Links & Policies | FOIA | Employee Info

U.S. Department of Health and Human Services Text

National Institutes of Health Text