The Black death was a devastating pandemic that hit Europe and Asia in the mid 1300's. It is said to be the most fatal pandemic ever recorded in history, sweeping over 25 million people.
This plague was believed to have been caused by the infection with the bacterium Yersinia Pestis. Other sources believe it was caused by a viral infection.
The consequences of this plague were many. It halted wars, trade, affected both nobility and the common man. Symptoms of this plague included high fevers and swellings (buboes).
Jews were blamed for the bubonic plague, perhaps because Jews carried FMF (familial Mediterranean fever) mutations and died at lower rates than other people. As a result antisemitism spiked, and Jews were burned at the stakes or killed.