Influenza likely originated thousands of years ago, with the first possible influenza epidemic occurring around 6,000 BC in China. Early descriptions of influenza-like illness appear in Greek writings from the 5th century BC
. The virus probably became a human disease when humans began domesticating animals such as birds and pigs, which provided conditions for zoonotic transmission and epidemics
. Regarding the 1918 influenza pandemic ("Spanish flu"), despite its name, the most likely site of origin was the United States, specifically Haskell County, Kansas, where an outbreak was recorded in January 1918. This hypothesis is supported by epidemiological evidence and the spread of the virus with American troops during World War I
. In summary:
- Influenza as a disease has ancient origins, possibly starting in China around 6,000 BC
- The virus likely crossed into humans through domesticated animals globally as agriculture developed
- The 1918 pandemic strain probably originated in the U.S., specifically Kansas
No single geographic origin can be pinpointed for influenza overall, but its emergence as a human pathogen is linked to early animal domestication and agriculture. The 1918 pandemic, the most devastating influenza outbreak in history, most likely began in the United States.
