black plague
The black plague or black death was a disease epidemic that spread throughout Europe in the mid 14th century. This was mostly due to the bubonic plague. The disease traveled through rat flea bites. Symptoms such as headache, fever, and swelling of lymph nodes were common and sometimes bloody sputum. When the plague was over, 1/3 to 1/2 of the European population was killed. Deaths caused riots, harsher persecution of Jews, and religious fanatics that would go about punishing themselves. The result was a major factor in the beginning of the renaissance.
The most deadly plague in human history is the black plague.