With billions upon billions of dollars to his name, you’d think Bill Gates would feel at least a little safer living in the Information Age. But as the 59-year-old Microsoft founder and philanthropist recently told Vox, that just isn’t the case.

“We've created, in terms of spread, the most dangerous environment that we've ever had in the history of mankind,” Gates said.

That isn’t because humans are more violent than before — we’re actually at our most peaceful, argues Harvard cognitive scientist Steven Pinker — or because our crops are genetically modified and our livestock survive on antibiotic-laced feed. Gates’ vision of our downfall is far more zoomed-in than that. Bill Gates says 33 million people could die within a year due to infectious disease.

“I rate the chance of a nuclear war within my lifetime as being fairly low,” he said. Lumped into that pot of unlikely events: death by volcanic eruptions, enormous earthquakes, and the kind of asteroids that offed the dinosaurs. However, “I rate the chance of a widespread epidemic, far worse than Ebola, in my lifetime, as well over 50 percent.”

“Far worse than Ebola” isn’t hyperbole. Given our planet’s history with pandemic disease outbreaks, including the Spanish flu from the early 20th century, H1N1 in 2009, and the recent cases of bird flu, which to date have spurred the mass slaughter of 39 million birds, Gates says his models predict a scenario in which tiny microbial invaders could feasibly wipe out 33 million people in just 250 days.

It isn’t just virulence that threatens humans’ safety. As last year’s Ebola outbreak demonstrated, the world simply isn’t prepared to contain an outbreak of that magnitude. The death toll from the virus between 2014 and 2015 was 10 times higher than every past Ebola outbreak combined.

More terrifying, Ebola’s reproduction number — a measure epidemiologists use to determine how many people an infected person will go on to infect — is on the low side. It’s just two. SARS, meanwhile, had a reproduction number of four and measles was a staggering 18. The fact Ebola managed to kill so many with such a middling reproduction number gives people like Gates cause for concern, especially since many diseases spread long before scientists have their finger on the pulse.

“If you look at the H1N1 flu in 2009,” Ron Klain, the so-called “Ebola Czar” who coordinated America’s response to the viral outbreak, told Vox, “it had spread around the world before we even knew it existed.” The same happened with the Spanish flu back in 1918. The virus didn’t come from Spain. Scientists don’t know where it came from — they only named it after the country because that’s where news of the outbreak first broke.

In reality, our progress as a species may be what’s spelling our downfall. Rates of immune-related disorders, such as asthma and allergies, are significantly higher in Western countries where there is an emphasis on cleanliness and sterility. This theory is known as the “hygiene hypothesis,” and it is gaining salience particularly as the conditions falling under its umbrella increase in prevalence. The Centers for Disease Control and Prevention finds allergies have been increasing steadily since the 1980s.

Turning these trends around requires a dedicated focus to improving the care given in a nation’s hospitals, where quarantines are taken seriously. But that demands the coordination from many moving parts, something the Ebola outbreak showed the U.S. lacked abundantly. Our technology is advancing considerably year over year. Without a way to use it effectively, it becomes useless, so humans become helpless.