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 in
Soldiers sick with Spanish flu at a hospital ward at Camp Funston in Fort Riley, Kansas
El Sol (Madrid), 28 May 1918: "The three-day fever – In Madrid 80,000 Are Infected – H.M. the King is sick"
Advertisement in The Times, 28 June 1918 for Formamint tablets to prevent "Spanish influenza"
Front page of The Times (London), 25 June 1918: "The Spanish Influenza"
An influenza pandemic is an epidemic of an influenza virus that spreads across a large region and infects a large proportion of the human population. There have been five major influenza pandemics in
Spanish flu
…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…
Influenza ward at Walter Reed Hospital, in Washington, D.C., during the 1918 flu pandemic
Estimates of hypothetical influenza deaths in the 2010 United States population (308,745,538 persons) across varying values of case-fatality ratio and the cumulative incidence of infection in the population. Selected estimated numbers of deaths are indicated with a black line, across each relevant combination of case-fatality ratio and cumulative incidence. In addition, the background color transitions from blue to yellow to red as the estimated absolute number of deaths increases. Case-fatality ratio is an example of a clinical severity measure and cumulative incidence of infection is an example of a transmissibility measure in the Pandemic Severity Assessment Framework.
Scaled examples of past influenza pandemics and past influenza seasons. Color scheme included to represent corresponding hypothetical estimates of influenza deaths in the 2010 US population, with the same color scale as the previous figure.
Influenza intervals in the CDC's Pandemic Intervals Framework