First of all, the Black Death killed a quarter of the world’s population. So jot that down. That is, in my opinion, a very bad and scary thing. Moreover, the virulence of the Black Death and mortality rates were actually a lot higher than that statistic would lead you to believe. The Black Death didn’t make it to the Americas or Australia, so that is the world’s death toll just from Asia, Africa, and Europe. That means mortality rates in areas with plague are actually much higher. In Florence, for example about sixty percent of the population died. That is bad.