Influenza, or flu, is a virus that attacks the respiratory system. The flu virus is highly contagious: when an infected person coughs, sneezes or talks, respiratory droplets are generated and transmitted into the air, and can then be inhaled by anyone nearby. Additionally, a person who touches something with the virus on it and then touches his or her mouth, eyes or nose can become infected. Before COVID-19, the most severe pandemic in recent history was the 1918 influenza virus, often called "the Spanish Flu". The virus infected roughly 500 million people - one-third of the world's population - and caused SO million deaths worldwide (double the number of deaths in World War I). In the United States, a quarter of the population caught the virus, 675,000 died, and life expectancy dropped by 12 years. With no vaccine to protect against the virus, people were urged to isolate, quarantine, practice good personal hygiene, and limit social interaction. The first observations of illness and mortality were documented in the United States (in Kansas) in March 1918 and then in April in France, Germany and the United Kingdom. To maintain morale, World War I censor minimized these early reports. Newspapers were free to report the epidemic'seffects in neutral Spain, such as the grave illness of King Alfonso XIII, and these stories created a false impression of Spain as especially hard hit. This gave rise to the name "Spanish Flu". Until February 2020, the 1918 epidemic was largely overlooked in the teaching of American history, despite the ample documentation at the National Archives and elsewhere of the disease and its devastation. The 100-year-old pictures from 1918 that just months ago seemed quaint and dated now seem oddly prescient.