It is usually passed between rodents, such as rats, mice, and squirrels, by the bite of an infected flea. The disease may be passed to people and cats by flea bites. People and cats may also get plague by coming in contact with animals that have plague or have died from the disease. People usually get it from a flea bite. It may cause swelling in the neck, under the arm, or in the groin area.
Septicemic plague occurs when the plague bacteria get into the blood.
This could happen through an open cut on the skin. People get very ill with this form of plague. Pneumonic plague is the least common, but most dangerous, form of plague. In this form, the bacteria get into the lungs and can be easily passed from one person to another through coughing and sneezing. Cats can get this form and pass it to people, also.