The 1918–1920 flu pandemic, also known as the Great Influenza epidemic or by the misleading name Spanish flu, was an exceptionally deadly global influenza pandemic caused by the H1N1 subtype of the influenza A virus. The earliest probable cases were documented in March 1918 in Haskell County, Kansas, United States, with further cases recorded in France, Germany and the United Kingdom in April. Two years later, nearly a third of the global population, or an estimated 500 million people, had been infected. Estimates of deaths range from 17 million to 50 million, and possibly as high as 100 million, making it one of the deadliest pandemics in history.