Skip to content
ContentLora

    Tip: press / anywhere to search.

    Explainer

    Plague explained: how it spreads, symptoms and treatment

    Plague is a bacterial infection caused by Yersinia pestis, which lives in small mammals and their fleas.[1] It is rare but still occurs: ten countries reported nearly 4,000 cases to WHO in 2019-2025.[2] Untreated pneumonic and septicaemic plague are always fatal, but antibiotics work well when given early.[3][4]

    Editor reviewedStrict sourcingUpdated ExplainerHealth and medicine, Life sciences

    Plague is a bacterial disease caused by Yersinia pestis, a bacterium that normally lives in small mammals and their fleas.[1] In the fourteenth century it was the “Black Death”, which killed more than 50 million people in Europe.[5] Today it is rare and treatable, but it still occurs. That is why the October 2026 death of a worker at a Siberian anti-plague institute drew so much attention (see our live tracker).[2][6] This page is general information, not medical advice. If you think you have been exposed or have symptoms, contact a clinician urgently.

    The three main forms

    Plague takes different forms depending on where the bacteria go in the body.

    • Bubonic plague is the most common form. It causes painful swollen glands called buboes.[7] Symptoms include sudden fever, chills, aches, weakness and vomiting.[8]
    • Pneumonic plague is a lung infection. It causes shortness of breath and a cough, often with bloody phlegm.[8]
    • Septicaemic plague is a blood infection. It can cause bleeding under the skin and blackened fingers, toes or nose.[9]

    WHO describes bubonic plague as the most common clinical form, with septicaemic and pneumonic plague less common but severe.[7] WHO gives an incubation period of one to seven days. The CDC gives 2 to 8 days for flea-borne bubonic plague and as little as about one day for pneumonic plague after inhalation.[10] Septicaemic disease can lead to organ failure, and tissue may die at the extremities.[9] Untreated, the bubonic form kills 30% to 60% of patients, and the pneumonic and septicaemic forms are always fatal.[3]

    How plague spreads

    Most people catch plague from a flea bite. People can also catch it by handling a sick or dead animal, or from sick pets, especially cats.[11] Only pneumonic plague passes between people, through droplets coughed into the air, and that usually needs close contact.[12]

    WHO lists three routes: infected flea bites, direct contact with infected tissue, and inhalation of infected respiratory particles.[13] Y. pestis persists in an enzootic cycle among wild rodents and their fleas. Human risk rises during or shortly after an epizootic, a die-off among animals.[14] WHO describes pneumonic plague as especially contagious, able to trigger severe epidemics through respiratory spread.[15] The CDC notes that droplet spread typically needs direct, close contact and has not been documented between people in the US since 1924.[12]

    Diagnosis and treatment

    Plague can only be confirmed by laboratory testing, ideally by finding Y. pestis in pus from a bubo, in blood or in sputum. A rapid dipstick test is widely used in Africa and South America.[16] Speed matters most. Untreated pneumonic plague can kill within 18 to 24 hours, but common antibiotics can cure it if given early.[4]

    CDC clinical guidance lists gentamicin and fluoroquinolones as first-line treatments in the US, usually for 10 to 14 days. It tells clinicians never to wait for test results before starting treatment.[17] Human evidence is limited. Several first-line drugs were approved on the basis of animal studies with limited human data, while doxycycline was tested against gentamicin in a randomised trial.[18] For people with close exposure to pneumonic plague, both the CDC and WHO describe a 7-day course of preventive antibiotics.[19]

    Prevention and vaccines

    The CDC’s advice for plague areas is to reduce rodent habitat, wear gloves when handling animals that may be infected, use insect repellent outdoors and keep fleas off pets. WHO adds avoiding flea bites and not handling animal carcasses.[20] Vaccines play a small role. WHO recommends them only for high-risk groups such as exposed laboratory staff, and the CDC says no plague vaccine is available in the US.[21]

    Where plague occurs today

    As an animal disease, plague is found on every continent except Oceania. Since the 1990s most human cases have been in Africa, and in 2019-2025 most cases reported to WHO were in the Democratic Republic of the Congo and Madagascar.[22] Madagascar records bubonic cases nearly every year in a season that runs from September to April.[23] In 2019-2025 ten countries reported nearly 4,000 cases and 423 deaths.[2] The US averages about five cases a year, more than 80% of them bubonic, mostly in northern New Mexico and Arizona.[24] The organism itself is profiled in yersinia-pestis. For another bacterial infection where hours matter, see our meningitis explainer.

    Next in the crash course

    Health & medicine

    Yersinia pestis (plague bacterium)

    Yersinia pestis is the bacterium that causes plague. How it cycles in rodents and fleas, how it infects people and where it is found today.

    More in Health & medicine

    Developing in Health

    Questions readers ask

    How do people catch plague?

    Most often from the bite of an infected flea. People can also be infected by handling infected animals or their tissues, through sick pets (especially cats), or by inhaling droplets from someone with pneumonic plague.[13][11]

    Can plague spread from person to person?

    Only the pneumonic form, through inhaled droplets, and this typically needs direct and close contact. The CDC says person-to-person spread has not been documented in the US since 1924.[12]

    Is plague curable?

    Yes, if treated early. WHO says common antibiotics can cure pneumonic plague if given early, and that recovery rates are high when treatment starts within 24 hours of symptoms.[4]

    Is there a plague vaccine?

    WHO recommends vaccination only for high-risk groups such as exposed laboratory staff and health workers. The CDC says no plague vaccine is available in the United States.[21]

    Where does plague still occur?

    In animals it is found on every continent except Oceania. In 2019-2025 most human cases reported to WHO were in the Democratic Republic of the Congo and Madagascar. The US averages about five cases a year, mostly in northern New Mexico and Arizona.[22][24]

    How soon do symptoms appear?

    WHO says usually after one to seven days. The CDC says pneumonic plague can appear in as little as about a day after inhaling the bacteria.[10]

    Sources

    · 24 claims from 5 publishers

    Each numbered claim is a statement we checked against the sources listed with it. Tap a number in the text to see its sources in place.

    1. [1]

      Plague is caused by the bacterium Yersinia pestis, which is usually found in small mammals and their fleas. confirmedas of 2026-10-11

      • Plague (fact sheet) · World Health Organization (retrieved 2026-10-11)
      • About Plague · US Centers for Disease Control and Prevention · 2026-08-24 (retrieved 2026-10-11)
    2. [2]

      Ten countries reported nearly 4,000 human plague cases and 423 deaths to WHO between 2019 and 2025. confirmedas of 2026-10-07

    3. [3]

      WHO puts plague's case-fatality ratio at 30% to 60% for the bubonic form and says pneumonic and septicaemic plague are always fatal when left untreated. confirmedas of 2026-10-11

    4. [4]

      Untreated pneumonic plague can be fatal within 18 to 24 hours of onset, but common antibiotics can cure it if given early; WHO says recovery rates are high when treatment starts within 24 hours of symptoms. confirmedas of 2026-10-11

    5. [5]

      Plague was known as the "Black Death" in the fourteenth century, when it caused more than 50 million deaths in Europe. confirmedas of 2026-10-11

    6. [6]

      A woman who worked at a laboratory of the anti-plague research institute in Irkutsk oblast, Siberia, died of severe pneumonia on 2 October 2026. confirmedas of 2026-10-06

    7. [7]

      Bubonic plague, marked by painful swollen lymph nodes called buboes, is the most common form; septicaemic and pneumonic plague are less common but severe. confirmedas of 2026-10-11

    8. [8]

      Bubonic plague typically causes sudden fever, chills, head and body aches, weakness, vomiting and nausea with painful lymph nodes; pneumonic plague causes severe respiratory symptoms such as shortness of breath and coughing, often with blood-tainted sputum. confirmedas of 2026-10-11

    9. [9]

      Septicaemic plague can cause bleeding under the skin, blackened dying tissue on fingers, toes and the nose, shock and organ failure. confirmedas of 2026-10-11

    10. [10]

      WHO says plague symptoms usually appear after an incubation period of one to seven days; the CDC gives 2 to 8 days for bubonic plague and as little as about one day for pneumonic plague after inhalation. confirmedas of 2026-10-11

    11. [11]

      The CDC says plague bacteria are most often transmitted by the bite of an infected flea, and people can also be infected by handling infected animals or through sick pets, especially cats. confirmedas of 2026-10-11

      • How Plague Spreads · US Centers for Disease Control and Prevention (retrieved 2026-10-11)
      • How Plague Spreads · US Centers for Disease Control and Prevention (retrieved 2026-10-11)
    12. [12]

      Inhaled droplets from a person or animal with pneumonic plague are the only way plague spreads between people, and this typically requires direct and close contact; the CDC says person-to-person spread has not been documented in the US since 1924. confirmedas of 2026-10-11

      • How Plague Spreads · US Centers for Disease Control and Prevention (retrieved 2026-10-11)
    13. [13]

      Plague spreads between animals and humans through the bites of infected fleas, direct contact with infected tissues and inhalation of infected respiratory particles. confirmedas of 2026-10-11

    14. [14]

      Y. pestis persists in cycles among wild rodents and their fleas, and people are usually at greater risk during or shortly after an outbreak among animals (an epizootic). confirmedas of 2026-10-11

      • How Plague Spreads · US Centers for Disease Control and Prevention (retrieved 2026-10-11)
      • How Plague Spreads · US Centers for Disease Control and Prevention (retrieved 2026-10-11)
    15. [15]

      WHO says pneumonic plague is especially contagious and can trigger severe epidemics through person-to-person transmission via respiratory particles. confirmedas of 2026-10-11

    16. [16]

      Confirming plague requires laboratory testing, ideally identifying Y. pestis in pus from a bubo, blood or sputum; a rapid dipstick antigen test is widely used in Africa and South America. confirmedas of 2026-10-11

    17. [17]

      CDC clinical guidance lists gentamicin and fluoroquinolones as first-line plague treatments in the US, typically for 10 to 14 days, and tells clinicians never to delay treatment while waiting for test results. confirmedas of 2026-10-11

    18. [18]

      CDC notes that some first-line plague antibiotics were approved by the FDA on the basis of animal studies with limited human clinical data, while doxycycline was compared with gentamicin in a randomised trial. confirmedas of 2026-10-11

    19. [19]

      CDC guidance says post-exposure antibiotics are indicated for close (under 6 feet), sustained contact with a pneumonic plague patient or contact with infected fluids, given for 7 days; WHO also recommends seven-day chemoprophylaxis for close contacts of pneumonic plague patients. confirmedas of 2026-10-11

    20. [20]

      CDC prevention advice for plague areas includes reducing rodent habitat, wearing gloves when handling potentially infected animals, using insect repellent outdoors and keeping fleas off pets; WHO advises avoiding flea bites and not handling animal carcasses. confirmedas of 2026-10-11

    21. [21]

      WHO does not recommend plague vaccination except for high-risk groups such as exposed laboratory staff and health workers, and the CDC says a plague vaccine is no longer available in the United States. confirmedas of 2026-10-11

    22. [22]

      As an animal disease plague is found on every continent except Oceania; since the 1990s most human cases have been reported in Africa, and in 2019-2025 most cases reported to WHO were in the Democratic Republic of the Congo and Madagascar. confirmedas of 2026-10-11

    23. [23]

      Madagascar records bubonic plague cases nearly every year during an epidemic season running from September to April. confirmedas of 2026-10-11

    24. [24]

      The US reports an average of five human plague cases a year (range 0-17), more than 80% of them bubonic, mostly in northern New Mexico and Arizona. confirmedas of 2026-10-07

    Revision history (1)
    1. Page created.

    Created Oct 11, 2026. Last reviewed by an editor on Oct 11, 2026. Next scheduled review: Jan 11, 2027.

    Cite this page

    "Plague explained: how it spreads, symptoms and treatment." ContentLora, updated Oct 11, 2026. https://contentlora.com/explain/plague-explained

    Spotted an error? Suggest a correction or emailcorrections@contentlora.com.

    ☰ Contents