The Black Death, or the Black Plague, the mid fourteenth century pandemic.

The Black Death, or the Black Plague, was one of the most deadly pandemics in human history, widely thought to have been caused by a bacterium named Yersinia pestis and spread by fleas with the help of animals like the black rat. It probably began in Central Asia[2] and spread to Europe by the late 1340s.

The total number of deaths worldwide from the pandemic is estimated at 75 million people; there were an estimated 20 to 30 million deaths in Europe. The Black Death is estimated to have killed between one-third and two-thirds of Europe's population.

The 14th century eruption of the Black Death had a drastic effect on Europe's population, irrevocably changing Europe's social structure. It was a serious blow to the Roman Catholic Church, and resulted in widespread persecution of minorities such as Jews, foreigners, beggars, and lepers.