The scenario was designed to be completely realistic, with a disease that could plausibly exist and a world that has the exact same resources to respond as we do now.
On May 15th, when the “Clade X” simulation was played out real-time, the people acting out the scenario were the sorts of individuals who’d be responding to this situation in real life. The players included former Senate Majority Leader Tom Daschle, Indiana Representative Susan Brooks (R), former CDC Director Julie Gerberding, and others with extensive experience.
Yet by the day’s end, representing 20 months after the start of the outbreak, there were 150 million dead around the globe, and 15 to 20 million deaths in the US alone. With no vaccine for the illness yet ready, that death toll would have been expected to climb.