Given the world's clunky response to the outbreaks of Ebola and the Zika virus recently, Mr Gates has his concerns about the planet's ability to successfully defend against a major epidemic - something that is certainly not out of the question given increasingly urgent threat of antibiotic resistant superbugs.
"I do think we'll have much better medical tools much better response (in the future) but we are a bit vulnerable right now if something spread very quickly like, say a flu that was quite fatal," he said.
"That would be a tragedy."
In 2014 Mr Gates and his wife Melinda pledged $US500 million ($721.8 million) to tackle infectious diseases in developing countries. They believe such work is critical in reducing instances of disease everywhere.
"The ebola epidemic has shown, once again, that in today's interconnected world, health challenges anywhere create health challenges everywhere," the Gates foundation said in a press release at the time.
"The best way to overcome those challenges is to dedicate ourselves to the great cause of reducing the global burden of infectious disease."