Napoleon visiting plague victims of Jaffa, Egypt in the late 18th century. Plague is a disease caused by the bacterium Pasteurella pestis and is transmitted by the rat flea. From the Middle Ages until the 20th century it caused regular, and sometimes vast, epidemics throughout the world. Napoleon Bonaparte, the French general and later Emperor, waged a disastrous campaign in Egypt - losing his fleet to the British and much of his army to disease. However he managed to convince the public at home it was a great French victory.