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Potentially life-threatening emergency
Bubonic plague
Other Resources UpToDate PubMed
Potentially life-threatening emergency

Bubonic plague

Contributors: Jacques Mather MD, MPH, Korin B. Hudson MD, Lewis Rubinson MD, PhD
Other Resources UpToDate PubMed


Infection with the gram-negative bacillus Yersinia pestis, commonly referred to as the plague, is a highly lethal disease that requires rapid, early recognition and prompt treatment. The bubonic form is the most common manifestation of this disease and often a consequence of inoculation via a break in the skin. It is characterized by the development of enlarged, painful, draining lymph nodes (called buboes) in conjunction with flu-like symptoms. Bubonic plague may progress to pneumonic and septicemic forms if left untreated. Untreated infections of all variants are highly lethal.

The most common reservoir for Y pestis is rodents (eg, prairie dogs, squirrels, chipmunks, rats), although cases involving dogs and cats have been described as well. The vectors are fleas, which feed on the infected animals and then can transmit the bacteria to susceptible hosts such as humans.

The incubation period for bubonic plague is typically about 4-7 days, and initial symptoms include malaise, myalgias, high fever, headache, and tachycardia. Then the patient will develop large, tender regional lymph nodes called buboes. The inguinal region is the most common site, but buboes can also form in the axillary and cervical lymph node basins. In advanced cases, these lymph nodes can open up and form suppurating wounds.

Untreated, bubonic plague can progress to septicemic and occasionally pneumonic plague in 2-6 days. The mortality rate of untreated bubonic plague can reach 60%. However, with treatment, mortality rates drop substantially to approximately 8%-10%. Drug resistance may become an important consideration. In 1995, a strain of multidrug-resistant (MDR) Y pestis was isolated from a bubonic plague patient in Madagascar. This strain was resistant to at least 8 antimicrobials, including streptomycin, tetracycline, chloramphenicol, and sulfonamides. To date, this is the only documented case of MDR Y pestis, although there is no systematic monitoring of resistance.

Endemic plague is seen in the southwestern United States (Colorado, New Mexico, Arizona, and California). About 10 cases are reported each year in the United States. Cases of plague also continue to be reported in much of Sub-Saharan Africa, parts of South America, and Asia. The incidence is likely higher than reported given that the majority of cases happen in underdeveloped regions of the world where diagnostic and reporting infrastructures are suboptimal.

People at higher risk for contracting bubonic plague include hunters, hikers, veterinarians, abattoir (slaughterhouse) workers, exotic pet owners, travelers to or residents of endemic areas, and those who live in rat-infested areas.

It is important to recognize that initial symptoms may resemble a typical cold with lymphadenopathy, and the clinician must have a high index of suspicion based on endemic locations, recent travel, and close contact with rodents or domestic animals that have recently become sick. Initial diagnosis in the emergency department for a single case may be difficult, unless the link to exposure is readily apparent and there is a readily apparent bubo. Some cases will be diagnosed after admission based on culture data (sputum or blood).

Rapid patient isolation, use of personal protective equipment for health care workers, antibiotic delivery, and notification of public health professionals are essential EARLY steps when the disease is suspected. If bioterrorism is suspected, the clinician should have a low threshold to activate the hospital incident command system and notify public health authorities.

In a bioterrorism event, intentional release of plague would most likely be in aerosol form, resulting primarily in the highly lethal and contagious pneumonic form of the disease. Bubonic plague could also occur. It is important to have a high index of suspicion for the possibility of a terrorist event when multiple people present with various forms of plague. Also, if someone presents with signs / symptoms suggestive of plague but has none of the expected natural exposures, then public health authorities should be contacted immediately. Once an intentional outbreak is confirmed, all patients with rapidly progressive pneumonia should be considered to have pneumonic plague unless an alternate diagnosis is found. Control measures and personal protective equipment for health care workers should be geared toward droplet transmission at a minimum.


A20.0 – Bubonic plague

50797007 – Bubonic plague

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Differential Diagnosis & Pitfalls

  • Cellulitis / ecthyma gangrenosum – often associated with disseminated pseudomonal infections
  • Tularemia – usually presents as a plaque with an eschar, pustule, or skin lesion, which is present distally to the involved lymph nodes
  • Mycobacterium marinum infection – usually presents with low-grade or absent fever and follows an indolent course
  • Bacterial adenitis – usually presents with a pustule or cellulitis-like skin lesion distal to the involved lymph nodes
  • Cat-scratch disease (Bartonella henseale) – can present with lymphadenopathy; almost always indolent without toxicity
  • Lymphogranuloma venereum (Chlamydia trachomatis) – presents with inguinal lymphadenopathy with buboes but few signs of systemic toxicity
  • Chancroid (Haemophilus ducreyi) – presents with enlarged, painless, inguinal lymph nodes
  • Necrotizing fasciitis

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Last Reviewed:02/12/2017
Last Updated:08/05/2021
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Potentially life-threatening emergency
Patient Information for Bubonic plague
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Contributors: Medical staff writer


Bubonic plague is an illness caused by the bacterium Yersinia pestis. This bacterium is carried by a certain type of flea, commonly known as a rat flea, which infects humans and animals. Humans can get bubonic plague from the bite of an infected flea, from the bite of an animal infected with Y. pestis, or from handling the carcass of an infected animal. The name of the illness comes from the classic skin lesions that develop in persons infected with Y. pestis: large, swollen lymph nodes called buboes.

Bubonic plague is easily treated with modern antibiotics, if the diagnosis is made quickly; this was not the case in the Middle Ages, when millions of people died from a bubonic plague epidemic. Today, bubonic plague exists around the world but in very small numbers. In the United States, there are 10-15 cases per year. Mortality, in disease that has undergone treatment, is about 5-15%; mortality, in disease that has been untreated, approaches 60%.

Yersinia pestis has the potential to be used as a weapon of bioterrorism; if this were to happen, the bacterium would likely be dispersed as an aerosol and would cause a different form of plague, known as pneumonic plague. Unlike bubonic plague, pneumonic plague is highly contagious among humans (bubonic plague is not contagious among humans), and mortality is even higher. In the case of a bioterrorism attack with Y. pestis, the United States maintains a stockpile of appropriate antibiotics to treat plague.

Who’s At Risk

Bubonic plague is usually passed to humans from the bite of an infected rat flea, which almost always infests rats, though other small rodents and even some domestic animals, such as cats and dogs, have been infected. In the United States, rat fleas are found in the Southwestern states. Other countries around the world with rat fleas and bubonic plague include India, Vietnam, parts of Africa, and the former Soviet Union. People at risk for acquiring bubonic plague include:
  • Travelers to the above endemic areas, particularly if residing in rat-infested areas
  • Hikers, particularly in endemic areas
  • Hunters, particularly in endemic areas
  • Animal slaughterhouse workers
  • People who live in rat-infested areas
  • Exotic pet owners who handle rats

Signs & Symptoms

The typical symptoms of bubonic plague infection are large, swollen, tender lymph nodes called buboes. These usually occur in the neck, armpit, and groin. Other symptoms include:
  • Fever
  • Feeling generally weak and achy (malaise)
  • Headache
  • Blister or infection at the site of a flea bite
  • Red or purple rash on top of the enlarged lymph nodes
Bubonic plague can evolve into septicemic or pneumonic plague; these people will look even sicker, with symptoms of weakness, confusion, abdominal pain, cough, chest pain, and presence of blood-tinged sputum.

Self-Care Guidelines

Bubonic plague is an unusual diagnosis and needs to be treated quickly, so if you have reason to suspect that you have bubonic plague, you should seek medical attention immediately and relay your concerns.

  • Although there is no evidence that bubonic plague is contagious between humans, take care to not come into contact with other people, particularly children, the elderly, and the immunocompromised.
  • Keep buboes and other skin lesions clean and covered.
  • Rest and stay well hydrated until you can receive direct medical care.

When to Seek Medical Care

You should contact your doctor whenever you have an illness with large, swollen lymph nodes. (Many medical conditions other than bubonic plague cause this sort of reaction, and most of these conditions require medical attention.) If you have a specific reason to suspect bubonic plague, mention your concerns to your doctor. If you are bitten by fleas in a rat-infested endemic area or if you are in contact with a person with bubonic plague, contact your doctor to discuss preventive treatment.


Common antibiotics are effective at treating bubonic plague, if started early in the course of illness. Your doctor will test your blood and will test the contents of the inflamed lymph node by taking a sample with a small needle. You will be started on antibiotics, and people in close contact with you may also be started on antibiotics to prevent against disease, though there is little risk of person-to-person transmission with bubonic plague.

There is no vaccine for bubonic plague.
Copyright © 2023 VisualDx®. All rights reserved.
Potentially life-threatening emergency
Bubonic plague
A medical illustration showing key findings of Bubonic plague : Chills, Headache, Axilla, Dead animal exposure, Lateral neck, Tachycardia, Wild animal exposure, Inguinal region, Myalgia, High fever, Rodent exposure
Clinical image of Bubonic plague - imageId=462254. Click to open in gallery.  caption: 'An umbilicated bulla with central crusting and surrounding erythema on the abdomen.'
An umbilicated bulla with central crusting and surrounding erythema on the abdomen.
Copyright © 2023 VisualDx®. All rights reserved.