It came in on the fur trade from Central America. Hit Iceland first, a year before it reached the continent of Europe.
The version I heard (believe it was on History Channel), was that it came from Central Kazakhstan, moved Westward through Russia (no record of the deaths in this part of the World), and moved onward to Turkey.
During a battle between the Turks and Venetians, the Turks began flinging the bodies of dead Turks over the walls of the Venetian fort.
Venetians returning to Italy brought the Plague back with them.
That's the story I heard. I'll have to "Google" the subject...
Furs from Central America? Really? How ratty.