Final answer:
The worst flu epidemic in the United States occurred in 1918, often referred to as the Spanish Flu. This pandemic infected millions worldwide and resulted in the deaths of an estimated tens of millions, including around 675,000 Americans.
Step-by-step explanation:
The worst flu epidemic in the US was in 1918, this event is commonly referred to as the Spanish Flu. This influenza pandemic occurred right around the end of World War I, and is considered the most lethal in recorded history. The virus was a new strain, believed to have resulted from a recombination of avian and human viruses, creating a new H1N1 virus. This strain spread rapidly worldwide, infecting an estimated one-third of the world's population and killing tens of millions of people. In the US, more than twenty million Americans fell ill, with around 675,000 dying from the disease. The pandemic finally ran its course in the spring of 1919.
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