Answer:
flea-infested rats
Step-by-step explanation:
The bubonic plague was one of the most devastating things that have ever happened to the human kind because of natural causes. This diseases was transported through the Silk Road from the Far Eastern ports. A type of flea was having this disease. The flea started to infest the animals, mostly the rats. The rats were everywhere, and they spread out the disease in Eurasia like a storm. The bubonic plague was a disease that the people of that time did not had any cure for. They were trying all sorts of methods but nothing seemed to work, and everyday there where lot of new deaths and infested people. The end result was a decimated population in Europe and parts of Asia, badly influencing the economies and military strength of the European nations.