American Expeditionary Force victims of the Spanish flu at U.S. Army Camp Hospital no. 45 in Aix-les-Bains, France, in 1918

Spanish flu

The 1918 influenza pandemic (January 1918 – December 1920) was an unusually deadly influenza pandemic, the first of the two pandemics involving H1N1 influenza virus. It infected 500 million people around the world, including people on remote Pacific islands and in the Arctic, and resulted in the deaths of 50 to 100 million (three to five percent of Earth’s human population at the time), making it one of the deadliest natural disasters in human history.