A pandemic is one of the world’s top three threats, and if not prepared for, could wipe out 30 million people in less than a year, philanthropist Bill Gates says.

Microsoft’s co-founder said at the Munich Security Conference in Germany Saturday that we’re due for an apocalyptic sickness on the scale of the 1918 flu, which killed some 50 million people. The global crisis could strike in the next 10-15 years if we’re not careful, Gates warned.

Bioterrorism has become feasible enough, he said, that a genetic engineer could use computers to create a synthetic airborne pathogen capable of wiping out a fraction of the world’s population quickly.

“The next epidemic could originate on the computer screen of a terrorist intent on using genetic engineering to create a synthetic version of the smallpox virus,” he said, “or a super contagious and deadly strain of the flu.”

But even if terrorists aren’t to blame, nature is likely to take its course.

“Whether it occurs by a quirk of nature or at the hand of a terrorist, epidemiologists say a fast-moving airborne pathogen could kill more than 30 million people in less than a year,” Gates said. “And they say there is a reasonable probability the world will experience such an outbreak in the next 10 to 15 years.”

Gates, who has been working to improve global health for 20 years, has long warned of such an outbreak, but the bio-terrorism angle appears to have sped up the “Doomsday Clock,” a symbolic warning of the likelihood of a global catastrophe.

Fears over pandemic have risen recently, as the World Health Organization reported in January that a new avian flu outbreak that was first detected late last year has affected at least 40 countries. Other strains of the virus have affected millions dating back to 2013.

Gates’ speech (an abridged version can be found at Business Insider) wasn’t all hell and high water. He said we’re underprepared for a global pandemic, but we have the technology to work on vaccines and other drugs. We just need the investment.

“I view the threat of deadly pandemics right up there with nuclear war and climate change. Innovation, cooperation, and careful planning can dramatically mitigate the risks presented by each of these threats,” Gates said. “I’m optimistic that a decade from now, we can be much better prepared for a lethal epidemic—if we’re willing to put a fraction of what we spend on defense budgets and new weapons systems into epidemic readiness.”

Correction: Gates said that a pandemic could wipe out 30 million people quickly, not 30 percent of the population.