Final answer:
The worst influenza epidemic of all time occurred from 1918 through 1919, during the end of World War I. It was caused by a new H1N1 virus that rapidly spread worldwide, claiming the lives of millions of people. This pandemic had a devastating impact on the American economy and resulted in a significant loss of life.
Step-by-step explanation:
The worst influenza epidemic of all time occurred from 1918 through 1919, during the end of World War I. It is commonly referred to as the Spanish Flu. This pandemic was caused by a new H1N1 virus that rapidly spread worldwide, claiming the lives of as many as 40 million to 50 million people, more than double the number of people killed in the war.
Conditions during World War I, such as crowding, poor sanitation, and rapid mobilization of personnel and animals, greatly contributed to the spread of the flu virus. The flu pandemic had a devastating impact on the American economy, shutting down mines, cutting telephone service, and forcing factories and offices to stagger shifts to avoid contagion.
By the time the pandemic finally disappeared after three waves, it is estimated that at least 675,000 Americans had died from the Spanish Flu.