One hundred years ago, a world recovering from a global war that had killed some 20 million people suddenly had to contend with something even more deadly: a flu outbreak. The pandemic, which became known as Spanish flu, is thought to have begun in cramped and crowded army training camps on the Western Front. The unsanitary conditions – especially in the trenches along the French border – helped it incubate and then spread. The war ended in November 1918, but as the soldiers returned home, bringing the virus with them, an even greater loss of life was just around the corner; between 50 million and 100 million people are thought to have died. The world has suffered many pandemics in the years since – at least three serious flu outbreaks among them – but no pandemic has been as deadly, nor as far-reaching.
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