In the mid-1300s, Europe experienced a period of crisis due to famine and plague. A famine from 1315-1317 due to climate changes weakened populations. Then, the Black Death plague arrived in 1347-1351, spread by fleas carrying bacteria. It originated in Genoa, Italy and caused fever, vomiting, and other symptoms. It killed between 25-75 million people, a third of Europe's population.