Answer:
Because in the 13th century there are no antibiotics to contain the disease.
Explanation:
Bubonic plague is a disease caused by bacteria. It is easily treated today, as we have a wide range of antibiotics. However, antibiotics were only discovered in the 20th century. In this case, before the 20th century, bubonic plague was a very dangerous disease and since it does not have a treatment to eliminate it, it became extremely violent, infecting people simultaneously and quickly.
