I think we have a winner...
Birth of the Black Plague: The Mongol Siege on Caffa
The spread of the plague through the ranks of the Mongols demoralized the army, and a large bulk of them lost interest in the siege. However, the Mongols would not back off, not without giving Caffa a piece of their own torment.
They put the corpses of their dead on their catapults and flung them over the defensive walls of Caffa.
The dwellers of Caffa watched as rotten bodies fell from the skies, crashing on their soil, spreading their putrid smell in all directions. The Christians could neither hide nor flee from the havoc that rained down upon them. They moved as many rotten bodies as they could, dumping them into the sea as quickly as they could. But by then, it was too late; the Black Death was already in Caffa.
The dwellers of Caffa watched as rotten bodies fell from the skies, crashing on their soil, spreading their putrid smell in all directions. The Christians could neither hide nor flee from the havoc that rained down upon them. They moved as many rotten bodies as they could, dumping them into the sea as quickly as they could. But by then, it was too late; the Black Death was already in Caffa.
The siege ended in 1347, after negotiations between the Mongols and the city, but by then the plague had begun its work.
Those who were still alive fled Caffa in ships sailing to Europe. They fled with their lives, taking the Black Death along with them. They made a stops Constantinople, unconsciously infecting the city. Thousands of people died in the ensuing disaster, including Andronikos, the son of John VI Cantacuzenos, a Greek Emperor.
Those who were still alive fled the city, but they fled too late. They fled in several directions away from Constantinople, taking the plague with them. By autumn, the western coast of Asia Minor was experiencing a major breakdown from the results of the dreadful pandemic.
The fleeing merchants would finally get to their homes in Italy, unaware of the death that followed them closely, like a shadow.