Mitől volt nagy durranás a Fekete halál pestisjárvány?

https://www.britannica.com/event/Black-Death/Effects-and-significance
https://www.nationalgeographic.com/history/history-magazine/article/fast-lethal-black-death-spread-mile-per-day
https://www.history.com/news/silk-road-black-death
https://www.history.com/topics/middle-ages/black-death