At the height of World War I, history’s most lethal influenza virus erupted in an army camp in Kansas, moved east with American troops, and then exploded worldwide, killing as many as 100 million people. It killed more in twenty-four months than AIDS killed in twenty-four years, more in a year than the Black Death killed in a century. It killed many more people than COVID-19, especially those who were young and otherwise healthy. This book, adapted from the #1 New York Times bestseller first published in 2004, shows young readers how this global tragedy came to pass; how science, war, and public policy collided; and how we might be able to prevent it from happening again. Impeccably researched and engrossingly told, this book provides young readers with historical and scientific context for epidemics that remains all too relevant today.