When you get the flu, viruses turn your cells into tiny factories that help spread the disease. In this animation, NPR's Robert Krulwich and medical animator David Bolinsky explain how a flu virus can trick a single cell into making a million more viruses. See and hear the rest of the story on NPR.org: http://www.npr.org/templates/story/story.php?storyId=114075029 Credit: Robert Krulwich, David Bolinsky, Jason Orfanon Copyright © 2009 NPR. All rights reserved. Visit our website terms of use for further information. https://www.npr.org/about-npr/179876898/terms-of-use For permission to reuse this video, visit our permissions pages at npr.org https://www.npr.org/about-npr/179881519/rights-and-permissions-information Follow NPR elsewhere, too: • Instagram: https://www.instagram.com/npr/ • TikTok: https://www.tiktok.com/@npr • Twitter: https://twitter.com/npr • Facebook: https://www.facebook.com/NPR