The Great Influenza: The Epic Story of the Deadliest Plague in History

by John M. Barry

Once the virus passed through a population, that population developed at least some immunity to it. Victims were not likely to be reinfected by the same virus, not until it had undergone antigen drift. In a city or town, the cycle from first case to the end of a local epidemic in 1918 generally ran six to eight weeks. In the army camps, with the men packed so densely, the cycle took usually three to four weeks. Individual cases continued to occur after that, but the explosion of disease ended, and it ended abruptly. A graph of cases would look like a bell curve—but one chopped off almost like a cliff just after the peak, with new cases suddenly dropping to next to nothing. In Philadelphia, for example, in the week ending October 16 the disease killed 4,597 people. It was ripping the city apart, emptying the streets, sparking rumors of the Black Death. But new cases dropped so precipitously that only ten days later, on October 26, the order closing public places was lifted. By the armistice on November 11, influenza had almost entirely disappeared from that city. The virus burned through available fuel. Then it quickly faded away.