The pandemic of bubonic plague that affected Europe from 1346 to 1353, often known as the Black Death, killed more than 20 million Europeans, almost one third of Europe's population at the time. The disease caused high fevers, vomiting, deliriousness and black boils that secreted blood and pus.
Genoese trading ships introduced the bubonic plague to Europe from the East, probably in China or the steppe region of Asia, after it first arrived in a Sicilian port. The disease quickly spread across Europe, following trade routes. It reached England in 1348 and Norway by 1349. Rumors reached Europe before the disease, as it ravaged it way across Asia during the early 1340s. These early rumors referred to the bubonic plague as the Great Pestilence.
In the 14th century, people did not understand how diseases such as the bubonic plague spread between people, making the Black Death all the more terrifying and panic-inducing. Many doctors refused to see patients, and trade temporary slowed to a halt. Even worse, the bubonic plaque also infected livestock animals, such as cows, sheep, goats, pigs and chickens. Some believed that the Black Death was a punishment from God for humanity's sins.
Subsequent bubonic plague epidemics followed the initial Black Death fairly frequently in the late Middle Ages, keeping population growth to a minimum. The smaller population actually led to an improvement in living conditions for the surviving laborers, who could now demand higher wages due to labor shortages.
The bubonic plague continues to occasionally infect some people, including in the United States. In 2015, 15 people contracted bubonic plague in the United States, and four died.