Bubonic plague is caused by the Yersinia pestis bacterium which is typically transmitted through the bites of infected fleas living on rodents like rats, squirrels, and prairie dogs. Symptoms include fever, chills, swollen lymph nodes, and other flu-like symptoms appearing 1-6 days after exposure. While not usually chronic, one can be reinfected, so prevention focuses on controlling rodent populations to limit flea-borne transmission of the plague bacterium.