In September 1918, a flu virus began spreading through Camp Devens, an overcrowded military base just outside Boston. By the end of the second week of the outbreak, one in five soldiers at the base had come down with the illness. But the speed with which it spread through the camp was not nearly as shocking as the lethality. “It is only a matter of a few hours then until death comes,” a camp physician wrote. “It is horrible. One can stand it to see one, two or 20 men die, but to see these poor devils dropping like flies sort of gets on your nerves. We have been averaging about 100 deaths per day.”

The devastation at Camp Devens would soon be followed by even more catastrophic outbreaks, as the so-called Spanish flu — a strain of influenza virus that science now identifies as H1N1 — spread around the world. In the United States, it would cause nearly half of all deaths over the next year. In what was already a […]