The 1918 flu hit the United States in three waves — a mild outbreak in the spring, the deadliest wave in the fall and a final spike when the virus returned that winter. All told, the pandemic infected a third of the world’s population and killed at least 50 million people, including at least 675,000 Americans.

One of them was the great-grandmother of Debbie Birx, the lead coordinator of the federal government’s coronavirus task force. “My grandmother, for 88 years, lived with the fact that she was the one, at age 11, who brought home flu to her mother … when her mother had just delivered,” said Birx, 63. “She never forgot that she was the child that was in school that innocently brought that flu home.”

Her middle name is Leah in honor of her great-grandma who succumbed to the deadliest outbreak in modern history. “This is why we keep saying to every American: You have a role to protect each and every person that you interact with,” Birx explained. “It’s why we are social distancing.”

The 1918 case study weighs on leaders of the public health community as they scramble to ramp up capacity and spur vaccine development in preparation for a sustained war against covid-19, the disease caused by the novel coronavirus. “We’re dealing with Cycle A right now, not the one that could come in the fall of 2020 – although we’re getting prepared for it by the innovations that are being worked on,” Birx said at the White House on Wednesday evening.