If everyone in the world were suddenly infected today and the onset would be, say, five days, the world would be in a mayhem in a week. The current fatality rate in countries such as Japan that doesn't have overloaded medical system, may seem low, but: 1) it's low because the system isn't overloaded. When overloaded, it starts to rise as the patients with heavy symptoms just die. 2) at a stage of a epidemic, it affects infra, which has feedback loop effects. 3) (for the sake of an argument) two percent of humanity is still 156 million people. A death sentence for 156 million people? That's harsh.