The bubonic plague in the Middle Ages, which was also called the Black Death, first hit Europe in 1347. The plague initially traveled from China via mice and rats travelling on trade ships between the continents. Plague started in Italy in Europe and quickly spread throughout the mainland, including the British Isles.
Within five years, the Black Death had claimed at least 20 to 25 million lives in Europe. Larger towns and cities, such as London, used mass graves to bury and contain the deceased citizens and prevent the disease from spreading further. At least 200 were buried in mass graves per day during the height of the pandemic. Death was also not confined to peasants, as members of the city council, government, and clergy caught the disease and died.
The disease took roughly one-third of the population of Europe during this initial spread. Plague could be spread through the air or directly from person to person. It was also carried by both fleas and rats, making it difficult to eradicate. However, at the time people did not know exactly how it was spread. While the disease was generally gone by the 1350s, recurrences happened regularly during the following centuries.