Plague is one form of infectious disease.
The Bubonic plague killed one third of Europe and much of Asia. I'm not sure there was such a thing as the "Numonic" plague. There is, however, something called pneumonic plague, which is a lung disease.
bubonic plague
This is history!
The Bubonic Plague.
It was a bacterium that caused it, but rats and fleas between them were the vector which spread the disease.
What Bubonic plague caused an rapid spreading disease
The Black Plague is a infectious disease.
Bubonic and septicemic plague are two of the three types of plague. The main difference between the two is that the bubonic plague cause extreme infection and swelling of the lymph nodes while the septicemic plague cause the body's clotting mechanism to stop.
Chronic means "present since a long time", like in "chronic disease". Contagious is something which can be easily communicated/transmitted to others. E.g. "Plague is a contagious phenomenon"
Disease
yes it is
xenopsylla cheopis is the scientific name of the flea that is the vector for Yersinia pestis, which is the bacteria that causes bubonic plague.