Learn how immunizing a critical portion of a community protects most members of the community.
Usually, healthcare providers diagnose the flu on the basis of whether it is epidemic in the community and whether the person's complaints fit the current pattern of symptoms. Healthcare providers rarely use laboratory tests to identify the virus during an epidemic. Health officials, however, monitor certain U.S. health clinics and do laboratory tests to determine which type of flu virus is responsible for the epidemic.
Last Updated March 24, 2010
Last Reviewed March 24, 2010