The Black Death was a devastating global epidemic of bubonic plague that struck Europe and Asia in the mid-1300s. It arrived in Europe in October 1347, when 12 ships from the Black Sea docked at the Sicilian port of Messina. Most sailors aboard were dead, and those still alive were gravely ill and covered in black boils that oozed blood and pus. Caused by the bacterium Yersinia pestis and spread by fleas on rats, the plague killed an estimated 30% to 60% of Europe's total population. This massive loss of life caused an immediate labor shortage, which fundamentally shifted the balance of power from land-owning nobles to the surviving peasantry. Higher wages and better working conditions followed, effectively ending the feudal system in many regions. The psychological and social impact of the plague also led to a rise in religious fervor and, paradoxically, a questioning of traditional authority that helped pave the way for the Renaissance.