Why the 1918 Flu Pandemic Never Really Ended

After infecting millions of people worldwide, the 1918 flu strain shifted—and then stuck around.

An unthinkable more than 50 million people worldwide died from the 1918-1919 flu pandemic commonly known as the “Spanish Flu.” It was the deadliest global pandemic since the Black Death, and rare among flu viruses for striking down the young and healthy, often within days of exhibiting the first symptoms. In the United States, the 1918 flu pandemic lowered the average life expectancy by 12 years. What’s even more remarkable about the 1918 flu, say infectious disease experts, is that it never really went away. After infecting an estimated 500 million people worldwide in 1918 and 1919 (a third of the global population), the H1N1 strain that caused the Spanish flu receded into the background and stuck around as the regular seasonal flu. But every so often, direct descendants of the 1918 flu combined with bird flu or swine flu to create powerful new pandemic strains, which is exactly what happened in 1957, 1968 and 2009. Those later flu outbreaks, all created in part by the 1918 virus, claimed millions of additional lives, earning the 1918 flu the odious title of “the mother of all pandemics.” Read more...

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