Plague, the disease caused by the bacterium Yersinia pestis, was the cause; The Y. pestis infection most commonly results in bubonic plague, but can also cause septicaemic or pneumonic plagues.
The Black Death was the beginning of the second plague pandemic.[10] The Black Death was a devastating global epidemic of bubonic plague that struck Europe and Asia in the mid-1300s. The plague arrived in Europe in October 1347, when 12 ships from the Black Sea docked at the Sicilian port of Messina. People gathered on the docks were met with a horrifying surprise: Most sailors aboard the ships were dead, and those still alive were gravely ill and covered in black boils that oozed blood and pus. Sicilian authorities hastily ordered the fleet of “death ships” out of the harbor, but it was too late: Over the next five years, the Black Death would kill more than 20 million people in Europe—almost one-third of the continent’s population.
Even before the “death ships” pulled into port at Messina, many Europeans had heard rumors about a “Great Pestilence” that was carving a deadly path across the trade routes of the Near and Far East. Indeed, in the early 1340s, the disease had struck China, India, Persia, Syria and Egypt.
The plague is thought to have originated in Asia over 2,000 years ago and was likely spread by trading ships, though recent research has indicated the pathogen responsible for the Black Death may have existed in Europe as early as 3000 B.C.
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