In recalling US involvement in World War I, one statistic is startling. Combat deaths for the US totaled 53,402. US military deaths from what was called Spanish flu totaled around 45,000. In 1918 some 675,000 Americans died from the Spanish flue. World War I killed some 20 million people. From 1918 to 1920 the Spanish flu killed between 50 and a hundred million people, three to five percent of the population of the Earth at the time. Speculations as to the origin point of the flu range from Kansas to China. The Great Influenza gained its name of the Spanish flu, due to strict wartime censorship of the devastating swathe which the Influenza cut in the nations at war. However, reporters were free to report on the mass mortality in neutral nations, and press coverage of the course of the Influenza in Spain produced sensational headlines throughout Europe and the US. Considering the mortality produced by the Great Influenza, it is strange how little it bulks in memory, at least until recently, compared to the purely man made disaster of World War I.
The severity of its symptoms make the current flu mild in comparison. It came in two waves in the US in 1918. The second wave, in the fall of 1918, suddenly vanished in November of that year in the US, almost certainly due to surviving strains being benign, and the deadlier strains having burned themselves out.