the black death
In November 1347 a Genoese ship returning from the Black Sea called at Naples on its route home. It brought the pestilence or great mortality to Europe.
The disease later called the Black Death because of the dark patches on the skin caused by subcutaneous bleeding was probably Bubonic Plague. Bubonic plague is carried by black rats, and spread to humans by the fleas that infest them. Human carriers could themselves pass on the infection through contact or the air.
The rapidity of the disease's spread not characteristic of modern outbreaks and the lack of contemporary reports of numerous dead black rats suggests that other diseases for example typhus may also have been involved