Black death

To date, the source of the outbreak has not been identified.

An excerpt from the article 15 facts about Black death

The plague is thought to have arrived in Europe from eastern or central Asia. The first documented cases were recorded in Crimea in 1347, where the plague most likely came via the Silk Road. The bacterium was spread by fleas that fed on the blood of rats that traveled aboard Genoese ships carrying slaves from Crimea to Europe.