What best explain the cause of the black death of the mid-1300?

The Black Death of the mid-1300s was primarily caused by the bacterium Yersinia pestis, which was transmitted to humans through fleas that infested rats. The disease spread rapidly along trade routes, particularly via ships, as well as through human contact. Poor sanitation, crowded living conditions, and a lack of medical knowledge exacerbated the outbreak, leading to high mortality rates across Europe and Asia. This catastrophic pandemic resulted in the deaths of an estimated 25 million people, significantly impacting society and the economy.