As soon as the citizens of Messina realized what horrible sickness had come aboard these ships, they expelled them from the port -- but it was too late. Plague quickly raged through the city, and panicking victims fled, thus spreading it to the surrounding countryside. While Sicily was succumbing to the horrors of the disease, the expelled trading ships brought it to other areas around the Mediterranean, infecting the neighboring islands of Corsica and Sardinia by November.
Meanwhile, plague had traveled from Sarai to the Genoese trading station of Tana, east of the Black Sea. Here Christian merchants were attacked by Tartars and chased to their fortress at Kaffa (Caffa). The Tartars besieged the city in November, but their siege was cut short when the Black Death struck. Before breaking off their attack, however, they catapulted dead plague victims into the city in the hopes of infecting its residents.
The defenders tried to divert the pestilence by throwing the bodies into the sea, but once a walled city had been struck by plague, its doom was sealed. As the inhabitants of Kaffa began to fall to the disease, the merchants boarded ships to sail home. But they could not escape the plague. When they arrived in Genoa and Venice in January of 1348, few passengers or sailors were left alive to tell the tale.
But few plague victims were all that was required to bring the deadly illness to mainland Europe.