The Bubonic Plauge
In Europe and Eurasia
The Bubonic Plauge...
...aka the Black Plague or Black Death, was one of the worst pandemics known to history. It started in Europe and Eurasia in the early 14th century, it peaked in the years 1346-1353. It reportedly brought the global population down from 450 million to 350 million. That is a 100 million death toll.
The Cause
The rapid spreading of Black Death can be attributed to rats. The rats carry the bacteria. The rats are then bitten by fleas, and the bacteria grows in its stomach. Those fleas then bite humans, transmitting the disease to them.
The effects and prevention
The Bubonic Plauge lowered the world's population by a large amount. It also lowered the already awful standard of living for the people in population dense cities. There are no cures to it, but it can be reduced by lowering the amount of rats in dense areas, thus lowering the chance of contracting the disease.