The 1918 flu pandemic (the "Spanish flu") was an influenza pandemic. It was an unusually deadly and severe pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin. Most victims were healthy young adults, in contrast to most influenza outbreaks, which predominantly affect juvenile, elderly, or weakened patients. The flu pandemic was implicated in the outbreak of encephalitis lethargica in the 1920s.
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Tissue samples from frozen victims were used to reproduce the virus for study. This research concluded, among other things, that the virus kills through a cytokine storm (overreaction of the body's immune system), which perhaps explains its unusually severe nature and the concentrated age profile of its victims. The strong immune system reactions of young adults ravaged the body, whereas the weaker immune systems of children and middle-aged adults resulted in fewer deaths.
Men in their 20's were the most severely affected.
Encephalitis Lethargica seems to be a variant of Narcolepsy, and is associated with strep infection.
