In 1924 Encyclopædia Britannica published a two-volume history of the 20th century thus far. More than 80 authors—professors and politicians, soldiers and scientists—contributed chapters to These Eventful Years: The Twentieth Century in the Making as Told by Many of Its Makers. But the book’s sprawling 1,300 pages never mention the catastrophic influenza pandemic that had killed between 50 million and 100 million people worldwide only five years earlier. And many history textbooks in subsequent decades just note the 1918–1919 flu pandemic as an aside when discussing World War I, if at all.