What did cities do differently?

The first flu deaths were reported in Boston on Sept. 8, 1918, the day before 300 sailors from the city arrived in Philadelphia. On Sept. 11, 19 sailors at Philadelphia's Navy Yard were sick. The numbers kept climbing.

Philadelphia officials knew about the flu in Boston and at the Navy Yard. The city’s bureau of health issued flu warnings and upgraded it to a reportable disease. Health officials said there was little chance it would spread among the public.

This doubt was embraced by many Philadelphians who “saw the war as the real priority and even characterized the hype of the flu as a ‘German ploy,’ ” historian Jeffery Anderson, who published his master's thesis on the pandemic at Rutgers, told USA TODAY.