How did the bubonic plague spread?

The bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea, Xenopsylla cheopis (the Oriental rat flea). Several flea species carried the bubonic plague, such as Pulex irritans (the human flea), Xenopsylla cheopis, and Ceratophyllus fasciatus.

How did the bubonic plague spread?

Plague bacteria are most often transmitted by the bite of an infected flea. During plague epizootics, many rodents die, causing hungry fleas to seek other sources of blood. Bubonic plague is transmitted through the bite of an infected flea or exposure to infected material through a break in the skin.

Symptoms include swollen, tender lymph glands called buboes. Buboes are not present in pneumonic plague. Humans can become infected when handling tissue or body fluids of a plague-infected animal. For example, a hunter skinning a rabbit or other infected animal without using proper precautions could become infected with plague bacteria.

This form of exposure most commonly results in bubonic plague or septicemic plague.