We Heard the Bells: The Influenza of 1918 - Department of Health and Human Services - January 2010 - In 1918-1919, the worst flu in recorded history killed an estimated 50 million people worldwide. The U.S. death toll was 675,000 - five times the number of U.S. soldiers killed in World War I. Where did the 1918 flu come from? Why was it so lethal? What did we learn? - Study materials are available at