How lethal was it? It was twenty-five times more deadly than ordinary influenzas. This flu killed 2.5 percent of its victims. Normally, just one-tenth of 1 percent of people who get the flu die. And since a fifth of the world’s population got the flu that year, including 28 percent of Americans, the number of deaths was stunning. So many died, in fact, that the average life span in the United States fell by twelve years in 1918.
