Bubonic transmission generally occurs in one of three ways:
- Direct contact with infected tissue or bodily fluids
- Bites from infected rodent fleas
- Inhaling infected droplets.
When a person becomes infected with the bacteria that cause plague, the bacteria begin to multiply within the body. For the bubonic variety, this occurs in the lymph system; for pneumonic plague, this occurs within the lungs. (The lymph, or lymphatic system, is a major component of your body's immune system. The organs within the lymphatic system are the tonsils, adenoids, spleen, and thymus.) After one to six days, symptoms of plague can begin. The period between becoming infected and the start of plague symptoms is called the plague incubation period.
Each type of plague has different symptoms. It is possible for a person to have symptoms of only one type; it is also possible for a person to experience symptoms from each of the types. For example, a person may first develop bubonic plague symptoms, followed several days later by septicemic plague symptoms, then pneumonic plague symptoms.
In order to make a bubonic diagnosis, the doctor will ask a number of questions about your medical history and will likely perform a physical exam. During the exam, the doctor will look at the skin and listen to the lungs for signs and symptoms of bubonic plague. If the doctor has a high suspicion that a person has bubonic plague, he or she will recommend certain tests.
Before making a definite diagnosis, the doctor will consider other possible conditions that share similar symptoms of plague. These conditions include:
- Shigellosis (an infectious disease typically caused by unsanitary conditions)
- Lymphogranuloma vernereum (a sexually transmitted disease affecting the lymph system)
- Syphilis (a sexually transmitted disease)
- Tularemia (a serious illness usually caused by animals)
- Cat scratch fever (a disease associated with being scratched by a cat)
- Typhoid fever (a life-threatening illness caused by Salmonella).