The US president incorrectly said the pandemic began in 1917, a year before the first cases were reported in 1918.
Speaking at a White House press conference, Mr. Trump suggested the illness had an impact on the conclusion of World War II, which lasted from 1939 to 1945.
Mr Trump made the remarks while discussing the current coronavirus pandemic, which has seen more than 163,000 people in the United States die from the virus.
The president was later escorted out of the briefing due to a shooting in front of the White House.
Mr Trump said: “The closest thing is in 1917, they say, the great pandemic was a terrible thing where they lost between 50 and 100 million people.
“Probably ended World War II. All the soldiers were sick. ”
The President continued: “It was a terrible situation and this [coronavirus] is very contagious, this one is very, very contagious. ”
A White House official later told USA Today that Mr. Trump was talking about World War I.
More people have died from the Spanish flu than in the fighting during this conflict, with the deployment of troops around the world likely contributing to its spread.
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But most historians don’t cite the pandemic as ending World War I, which ended when Germany signed an armistice, after suffering a considerable number of combat casualties as the strategic balance shifted from decisively in favor of the Allies.
Although it’s commonly known as the Spanish flu, experts have since said it’s more likely to have started in the US, UK, China or France.
It became commonly associated with Spain because the neutral country did not have a wartime censorship that prevented reporting of the disease.
Mr. Trump has been criticized for his response to the COVID-19[feminine[feminine epidemic, with critics claiming it was downplaying the disease and its refusal to take stronger and faster action helped the United States to record the highest death toll in the world.