The Bill and Melinda Gates Foundation is part of the Coalition for Epidemic Preparedness Innovation (CEPI). CEPI focuses on creating vaccines that could stop the outbreak of future diseases.

And while the organisation has about $US700 million ($927 million) to work with, Gates worries it won't be enough to stop another related, impending threat.

"Bio-terrorism," or the purposeful spread of epidemics, could become a serious issue, and Gates says we need to start figuring out how to combat it now.

"What preparedness will look like for intentionally-caused things, that needs to be discussed," he said. "It's very hard to rate the probability of bio-terrorism, but the potential damage is very, very huge."

Gates spoke about the dangers of both intentional and natural epidemics at a World Economic Forum event earlier in the week, and he will be discussing the issue in detail at a Munich conference in February.

"I think an epidemic, either naturally caused or intentionally caused, is the most likely thing to cause, say, 10,000 excess deaths," Gates said.

He voiced the same concern in March during a Reddit Ask Me Anything (AMA) session: "The problem of how we prevent a small group of terrorists using nuclear or biological means to kill millions is something I worry about," he wrote.

Gates' message is beginning to be taken seriously, at least among his tech peers. Sam Altman, president of Silicon Valley startup accelerator program Y Combinator, told The New Yorker's Tad Friend that he occasionally discusses how the world will end with peers.

One of their most popular theories, he says, is bio-terrorism.

"After a Dutch lab modified the H5N1 bird-flu virus, five years ago, making it super contagious, the chance of a lethal synthetic virus being released in the next twenty years became, well, nonzero," Altman said.

Gates says that in order to prevent bio-terrorism, governments will need to get involved and work together. Because epidemics "don't respect borders."

"It's tricky because this is a global problem. So, how do countries work together, and which countries should put up which resources?" Gates said. "Whether you're looking at this through a humanitarian sense or a purely domestic sense, [combatting epidemics] are investments that should be made."

This story first appeared in Business Insider. Read it here or follow BusinessInsider Australia on Facebook.