In 1918, while World War I (WWI) raged overseas, Americans on the home front fought their own battle against an uncontrollable strain of influenza. The Spanish influenza epidemic spread quickly in the United States (U.S.) and abroad as it devastated civilian populations and military combatants. Soldiers transmitted the virus in their close living quarters and circulated it around the world as they travelled from base to base. Approximately 45,000 American service members died of influenza during WWI, nearly half of all American casualties. Eventually, the Spanish flu claimed over 650,000 lives in the U.S., just a fraction of its 20 to 50 million global victims.