Southern Europe
From Tardis Wiki, the free Doctor Who reference
Following the 1346 siege of Kaffa, in which Janibeg Khan's Mongol army introduced the bubonic plague to the city, Genoese merchants took the disease to the Mediterranean ports of southern Europe from where it spread throughout the continent, eventually killing a third of the population. (PROSE: Bunker Soldiers [+]Loading...["Bunker Soldiers (novel)"])