Plague is an acute, infectious disease of humans, rodents, and ectoparasites (fleas, lice).
Bubonic plague is caused by bacteria called
Yersinia pestis. These bacteria are found mainly in rodents, particularly rats, and in the fleas that feed on them. Other animals and humans usually contract the bacteria from rodent or flea bites.
(Click Plague and Animals for more information.)
Usually, bubonic plague is spread by being bitten by an infected flea or rodent. In rare cases,
Yersinia pestis bacteria that is present on a piece of contaminated clothing or other material used by an infected person may enter through an opening in the skin. The bacteria are rarely spread from person to person.
When a person becomes infected with the bacteria that cause bubonic plague, the bacteria begin to multiply within the lymph system. (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 two to six days,
symptoms of bubonic plague can begin. The period between becoming infected and the start of symptoms is called the incubation period.
In order to make a 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 the disease, he or she will recommend certain tests.
Before diagnosing bubonic
plague, however, the doctor will consider other possible conditions, because several conditions share similar
symptoms of plague. These conditions include:
- Syphilis (a sexually transmitted disease)
- Lymphyogranuloma vernereum (a sexually transmitted disease affecting the lymph system)
- Appendicitis
- Hernia
- Tularemia (a serious illness usually caused by animals)
- Cat scratch fever (a disease associated with being scratched by a cat)
- Shigellosis (an infectious disease typically caused by unsanitary conditions)
- Typhoid fever (a life-threatening illness caused by Salmonella).
Treatments for Bubonic Plague
When bubonic plague is suspected, the person should be hospitalized and placed in isolation. Even before lab tests come back,
treatments for bubonic plague will be started, typically involving antibiotics and supportive care. Supportive care is treating symptoms and complications that occur as a result of bubonic plague. It also important that people who have been in close contact with a bubonic plague patient be identified and evaluated for possible treatment.
If bubonic plague is left untreated, the bacteria can quickly multiply in the bloodstream, causing
septicemic plague, or even progress to the lungs, causing
pneumonic plague. The bubonic plague mortality rate is 50 to 90 percent if not treated; the mortality rate is 15 percent when the disease is diagnosed and treated early.
How Common Is Bubonic Plague?
Approximately 10 to 20 people in the United States develop bubonic
plague each year from flea or rodent bites -- primarily from infected prairie dogs -- in rural areas of the southwestern United States. About one in seven of those infected die from it. There has not been a case of person-to-person infection in the United States since 1924.
Worldwide, there have been small bubonic plague outbreaks in Asia, Africa, and South America. Globally, the World Health Organization (WHO) reports 1,000 to 3,000 cases of plague every year. Current WHO statistics show there were 2,118 cases in 2003 worldwide.
Bubonic plague occurs more frequently during the spring and summer months, especially in males and people under the age of 20.
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