Pandemic occurred in three waves in the United States throughout 1918 and 1919. One-stop access to U.S. Government avian and pandemic flu information. Article about the Influenza pandemic with a look to geographical origins and social impact. The 1918 flu pandemic (commonly referred to as the Spanish Examines the worst epidemic the U.S. has ever known, which killed more Americans than all the combat deaths of the 20th Century combined.The 1918 flu caused the highest number of known flu deaths worldwide, estimated To the contrary, the 1918 pandemic spread more or less simultaneously in 3 . .