The Black Death.

Bubonic plague is caused by the bacterium Yersinia Pestis. It's commonly to find in wild rodents such as rabits and hares,wild carnivores and domestics cats.

Symtoms are fever,headache,chills,fatigue,dizziness and metallic taste.A few hours or days,appears the bubon,from one or ten cm,which is usually in the groin,armpits,neck and sometimes start to suppore.When you touch the bubon,it's hurts.
The first pandemic occurred in ancient Egypt and killed 50 or 60 % of the population of North Africa,Central and South Asia.

The second pandemic was in 1346,called the Black Death.The Black Death started in China or Central Asia. The plague travelled to Crimea. From there,it was carried by Oriental rats fleas living on merchant ships. On having realized that the fleas were the principal transmisors of the Black Death,they took measurements,since the clothes of the infected were burned,or they prohibit the entry of merchant ships in the cities,also they burn the infected dead men. This occasioned twenty-five millions deaths,the agricultural production decreases and the mean age disappeared.