We were warned in 2012, when the Rand Corporation surveyed the international threats arrayed against the United States and concluded that only pandemics posed an existential danger, in that they were “capable of destroying America’s way of life.”

We were warned in 2015, when Ezra Klein of Vox, after speaking with Bill Gates about his algorithmic model for how a new strain of flu could spread rapidly in today’s globalized world, wrote that “a pandemic disease is the most predictable catastrophe in the history of the human race, if only because it has happened to the human race so many, many times before.” If there was anything humanity could be certain that it needed to prepare for to prevent the deaths of a lot of people in little time, it was this.

We were warned in 2017, a week before inauguration day, when Lisa Monaco, Barack Obama’s outgoing homeland-security adviser, gathered with Donald Trump’s incoming national-security officials and conducted an exercise modeled on the administration’s experiences with outbreaks of swine flu, Ebola, and Zika. The simulation explored how the U.S. government should respond to a flu pandemic that halts international travel, upends global supply chains, tanks the stock market, and burdens health-care systems—all with a vaccine many months from materializing. “The nightmare scenario for us, and frankly to any public-health expert that you would talk to, has always been a new strain of flu or a respiratory illness because of how much easier it is to spread” relative to other pandemic diseases that aren’t airborne, Monaco told me.

We were warned in 2018, on the 100th anniversary of the flu pandemic of 1918, which killed 50 to 100 million people around the world.