1918 flu death toll: estimates run from 17 to 100 million

The 1918 influenza pandemic killed somewhere between about 17 million and 100 million people worldwide in 1918–20, depending on whose estimate you use. The U.S. Centers for Disease Control and Prevention puts it at at least 50 million, including about 675,000 Americans.

The range is that wide because much of the world kept no reliable records. Deaths went unregistered, misdiagnosed or uncertified, so every global total is a reconstruction from partial data. The published estimates have moved up and then down:

Estimate	Global deaths
1920s calculation	about 21.5 million
1991 paper	24.7–39.3 million
Johnson & Mueller, 2002	about 50 million, possibly up to twice that
Spreeuwenberg et al., 2018	17.4 million

The 2018 study, from the Dutch research institute NIVEL, worked from mortality databases for 13 countries plus records from British India, controlled for wartime deaths, and concluded that totals above 25 million are not realistic. That is well below the 50 to 100 million of other recent estimates, and the CDC’s 50 million remains the most cited number.

The comparison with the war holds either way. The U.S. National Archives puts deaths in the First World War at about 16 million, so even the lowest pandemic estimate edges past it, and the usual one is about three times as large. The two overlapped: the virus was spreading in 1918, the year the war ended with the armistice.

The sources disagree on infections too: the CDC says about 500 million people, a third of the world, caught it; the National Archives says a fifth. They agree on its oddest feature. Alongside the very young and the elderly, it killed large numbers of healthy 20-to-40-year-olds, and U.S. life expectancy fell by 12 years in a single year.