Just over a century ago, a calamitous influenza outbreak swept across the globe, infecting a fifth of the world’s population and killing between 50 million and 100 million people in the space of a year.

It’s easy to assume that modern medicine protects humankind from the likes of 1918’s devastating Spanish flu. But experts warn that the world’s much larger population—increasingly connected both geographically and economically—is more vulnerable now than ever.

“In those days we didn’t have airplane flights happening a thousand times a day with stocks being traded electronically around the world,” said Martin Friede, PhD, who leads the World Health Organization (WHO) Initiative for Vaccine Research in Geneva, Switzerland.

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Read more at JAMA…