Sure, humankind may ends in all sorts of unlikely catastrophic ways: giant volcano explosion, earthquake, asteroid, nuclear wipe out. But Bill Gates isn’t too concerned with most of those. He’s more concerned about a “well over 50 percent” likelihood of an apocalyptic infectious flu epidemic.

In a conversation with Vox about humanity’s next “nightmare scenario,” Gates elaborated on how this nightmare might just come to life. Throughout history, there hasn’t been many examples of infectious flus that are both widespread and high in mortality rates. The Spanish Flu of 1918 was the first instance of it--and the Spanish Flu is nothing compared to the impact a similar breakout would have today. Our interconnectedness, our dense urban centers, and the ease and speed of travel means devastating consequences.

Bill Gates was worried enough to fund an “eye-opening” computer simulated disease modeling group to see how the numbers would play out. What he learned? “This is the greatest risk of a huge tragedy to kill over an excess of 10 million people in a year.”

And, according to everyone’s favorite super-billionaire: we’re not ready. The Ebola outbreak was a warning sign, evidence of our lack of preparation in the face of a serious epidemic. So stop spending money on military forces and start thinking about how to prevent a The Stand-esque wipeout, everyone. The end may be soon to come.