What is the primary cause of the bubonic plague?

The primary cause of the bubonic plague is a bacterial disease transmitted by fleas. Specifically, the bacterium Yersinia pestis is responsible for the disease, which predominantly affects rodents but can also be transmitted to humans through bites from infected fleas. The fleas act as vectors, carrying the bacteria from the rodents to other hosts, including humans. When a flea bites a host, it can introduce the bacteria into the bloodstream, leading to the characteristic symptoms of the bubonic plague, such as swollen lymph nodes (buboes), fever, and chills. Understanding this transmission route highlights the importance of controlling rodent populations and flea infestations to prevent outbreaks of the plague.