CDC Centers for Disease Control and Prevention Influenza Flu Homepage U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS the surveillance methods in the Flu Activity section of the CDC Influenza CDC Centers for Disease Control and Prevention Influenza Flu Homepage About the Flu. Key Facts About Flu Key Facts About the Flu. Symptoms, what to do if flu season, the disease Flu Activity Updated! Jan 7 Find the latest news stories, overviews, research and more on Influenza from MedlinePlus, the National Library of Medicine's consumer health site. MedlinePlus, the National Library of Medicine's consumer health site. Influenza, Flu, Grippe, Avian Influenza, Bird Flu, Fowl Plague, Communicable Diseases