Lasting from June 1918 to December 1920, the Spanish flu killed between 50 and 100 million. This made it one of the deadliest natural disasters in human history. This doesn't include the 500 million that were infected. While we cannot pinpoint one certain location that it originated in we know that it spread all around the world. Some sample tissues were saved in order to recreate this infection. When this was done it was discovered that it kills via a cytokine storm, meaning an overreaction of the body's immune system, which would explain the target age (young adults) and the severity of it. Modern transportation was the cause of its wide spread reaction.
