There are many theories that explain the onset of Plague, but all of them agree that the main source was China, Mongolia, as well as the Hunan province.
It has not been decided yet whether it was a bubonic plague or not. Besides, people debate if it was caused by rats or not. However, there is no exact answer.
There were three kinds of plague: bubonic, pneumonic and septicemic. People that are affected by bubonic plague feature the lymph notes, neck, groin and armpits most affected. The symptoms of this disease are: fevers, headaches and vomiting.
The pneumonic synonyms are the reddish bloody and slimy sputum. The septicemic plague features the DIC markings (skin turning purple). It id also rather interesting to mention that the plague could no be ascertained when it began.
According to the accounts of both Mussis and the bull of Pope Clement VI, the plague was a God judgment on people.
However, according to Herman Gigas, some people thought the plague was the corruption of the air. Besides, others said that it was the Jews who had planned to wipe out all the Christians with poison and as a result, they had poisoned wells and springs. That is why the city councilors or the pope tried to protect the Jews as many people wanted to kill them all. But is some places under torture many Jews confessed having brought spiders and other insects in the pots. Besides, those Jews said that not every Jew had known that, only the most important ones.
Anyway, People of different faiths were blamed for things that they never did, for example, the act of terrorism.
1) “Blaming people in the Black Death” Random, 2008
2) Crisis and Renaissance