The black death also known as the bubonic plague was a bacterial infection called Yersinia Pestis. It was transmitted by fleas that were on rats . ( You got it from the bite of an infected flea or rodent). Since there were lots of trading going around, the rats got on the boats infected the sailors and when the ship stopped the rats hoped of and went into the town. The towns were packed together and had extremely poor hygiene and filthy streets. You were practically guaranteed to get it. If you were a peasant because you were poor . The fleas jumped form one host to the other. Half of the European population died form the plague.
