A version of this story appears in the of National Geographic magazine.Philadelphia detected its first case of a deadly, fast-spreading strain of influenza on September 17, 1918. The next day, in an attempt to halt the virus’ spread, city officials launched a campaign against coughing, spitting, and sneezing in public. Yet 10 days later—despite the prospect of an epidemic at its doorstep—the city hosted a parade that 200,000 people attended.Flu cases continued to mount until finally, on October 3, schools, churches, theaters, and public gathering spaces . Just two weeks after the first...…A version of this story appears in the of National Geographic magazine.Philadelphia detected its first case of a deadly, fast-spreading strain of influenza on September 17, 1918. The next day, in an attempt to halt the virus’ spread, city officials launched a campaign against coughing, spitting, and sneezing in public. Yet 10 days later—despite the prospect of an epidemic at its doorstep—the city hosted a parade that 200,000 people attended.Flu cases continued to mount until finally, on October 3, schools, churches, theaters, and public gathering spaces . Just two weeks after the first...WW…