Health Topic

Plague

Plague is an infection caused by bacteria found mainly in rats and in the fleas that feed on them. There are three forms of plague.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Bubonic plague · Pneumonic plague

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Plague

Plague is an infection caused by the bacterium Yersinia pestis. The bacteria are found mainly in rats and in the fleas that feed on them. People and other animals can get plague from rat or flea bites. In the past, plague destroyed entire civilizations. Today plague is uncommon, due to better living conditions and antibiotics.

There are three forms of plague:

  • Bubonic plague causes the tonsils, adenoids, spleen, and thymus to become inflamed. Symptoms include fever, aches, chills, and tender lymph glands.
  • In septicemic plague, bacteria multiply in the blood. It causes fever, chills, shock, and bleeding under the skin or other organs.
  • Pneumonic plague is the most serious form. Bacteria enter the lungs and cause pneumonia. People with the infection can spread this form to others. This type could be a bioterror agent.

Lab tests can diagnose plague. Treatment is a strong antibiotic. There is no vaccine.

It sits within Infections.

The lead U.S. institute for this subject is the National Institute of Allergy and Infectious Diseases.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Plague

26 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Symptoms

Diagnosis and Tests

Prevention and Risk Factors

Statistics and Research

Medical subject headings

Clinicians and researchers index this subject under Plague. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Plague, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.