Historians do not fully agree on exactly where the 1918 “Spanish flu” started, but the leading theories point to Kansas in the United States, northern China, or military camps in Europe, not Spain.

Why it’s called “Spanish” flu

  • The pandemic became known as “Spanish flu” mainly because Spain, a neutral country in World War I, had a free press that openly reported on early outbreaks and the illness of King Alfonso XIII, while warring countries censored news of the disease.
  • As a result, many people wrongly assumed Spain was the origin, even though evidence suggests the virus was already circulating elsewhere.

Main origin theories

  • Kansas, USA (Fort Riley theory)
    • One of the first clearly documented large outbreaks occurred at Fort Riley, Kansas, on 11 March 1918, when hundreds of soldiers fell ill within a week.
* Overcrowded, unsanitary army camps and rapid troop movements to Europe could have helped spread the virus worldwide.
  • Northern China and Chinese laborers
    • Some researchers argue a severe respiratory outbreak in northern China in late 1917 matched what was later recognized as the Spanish flu.
* Tens of thousands of Chinese laborers were then transported across the world to work behind Allied lines, potentially carrying the virus along routes through North America and Europe.
  • European military camps (France/UK)
    • Other historians point to unusual, very deadly respiratory outbreaks in 1917 in military hospitals in northern France and in Aldershot, England, which resemble early Spanish flu–like disease.
* This view suggests a European origin, with the virus emerging in 1915–1916 and evolving in soldiers before exploding globally in 1918.

What modern science says

  • Genetic and evolutionary analyses show the 1918 H1N1 virus likely came from an avian-like influenza virus that adapted to humans shortly before 1918, but they do not pinpoint a single geographic starting point.
  • Overall, current scholarship treats the precise place of origin as uncertain; Kansas, northern China, and European military camps remain the main contenders, while Spain is considered an unlikely starting point.

Information gathered from public forums or data available on the internet and portrayed here.