This site is currently implementing core features and is not ready for patient use yet.
This site is currently implementing core features and is not ready for patient use yet.
For informational purposes only — not medical advice
How serious?
Risk of death
No
Vaccine available?
Time to symptoms
Countries affected
Active outbreaks
Extremely rare in travelers. Endemic foci exist in Madagascar, Democratic Republic of Congo, and parts of the American West. Avoid contact with rodents and fleas. If you develop sudden high fever with painful lymph nodes or cough after potential exposure, seek emergency care immediately.
Severe bacterial infection caused by Yersinia pestis, transmitted by infected flea bites or respiratory droplets. Three clinical forms: bubonic, septicemic, and pneumonic. Treatable with antibiotics if diagnosed early; untreated pneumonic plague is nearly always fatal.
Symptoms | Frequency | Severity | Onset |
|---|---|---|---|
| Fever | 95% | Moderate | Early |
| Swollen lymph nodes | 85% | Severe | Early |
| Chills | 85% | Mild | Early |
| Headache | 80% | Moderate | Early |
| Malaise | 80% | Mild | Early |
| Myalgia | 55% | Mild | Early |
| Loss of appetite | 60% | Mild | Early |
| Hemoptysis | 5% | Severe | Peak |
| High fever | 65% | Moderate | Peak |
| Bruising | 12% | Moderate | Peak |
| Chest tightness | 6% | Moderate | Peak |
| Cough | 15% | Moderate | Peak |
| Hepatomegaly | 20% | Mild | Peak |
| Petechiae | 15% | Moderate | Peak |
| Shortness of breath | 8% | Severe | Peak |
| Splenomegaly | 15% | Mild | Peak |
| Tachycardia | 50% | Moderate | Peak |
| Abdominal pain | 25% | Mild | Peak |
| Vomiting | 35% | Mild | Peak |
| Diarrhea | 15% | Mild | Peak |
| Hypotension | 25% | Severe | Late |
| Confusion | 10% | Severe | Late |
| Fatigue | 70% | Mild | Any phase |
| Nausea | 45% | Mild | Any phase |
Plague is an acute, severe, and potentially fatal zoonotic infection caused by the gram-negative bacterium Yersinia pestis. One of the oldest known epidemic diseases, plague has caused three devastating pandemics in human history: the Justinianic Plague (541-750 CE), the Black Death (1346-1353, killing an estimated 25-50 million in Europe), and the Third Pandemic (1855-1960, originating in China).
Y. pestis is maintained in sylvatic (wild) rodent reservoirs worldwide and transmitted to humans primarily through the bite of infected fleas, particularly Xenopsylla cheopis (the oriental rat flea). The bacterium can also be transmitted by direct contact with infected animal tissues or, critically, by respiratory droplets from patients with pneumonic plague.
Plague manifests in three principal clinical forms: bubonic (80-95% of cases), septicemic, and pneumonic. Without treatment, bubonic plague has a case fatality rate of 30-60%, while untreated pneumonic and septicemic plague are nearly 100% fatal. With prompt antibiotic therapy initiated within 24 hours of symptom onset, the CFR drops to less than 10%.
Plague remains endemic in parts of Africa (particularly Madagascar and the Democratic Republic of Congo), Asia, South America, and the western United States. Between 2010 and 2015, the WHO reported 3,248 cases and 584 deaths worldwide. It is classified as a WHO-notifiable disease and is also considered a Category A bioterrorism agent by the CDC due to its potential for weaponization in aerosol form.
Clinical Overview
Plague is a rapidly progressive infectious disease that constitutes a public health emergency whenever it occurs. Early recognition and treatment are paramount for survival.
Key Clinical Facts:
Causative agent: Yersinia pestis (gram-negative coccobacillus, family Yersiniaceae)
Transmission: Flea bite (primary), direct contact with infected tissues, respiratory droplets (pneumonic form)
Reservoir: Wild rodents (prairie dogs, ground squirrels, rats, gerbils)
Incubation period: Bubonic 2-8 days; pneumonic 1-3 days (can be as short as hours)
Case fatality rate: Untreated bubonic 30-60%, untreated pneumonic/septicemic ~100%; treated <10%
Treatment: Aminoglycosides (gentamicin, streptomycin), doxycycline, fluoroquinolones
Clinical Forms:
Public Health Significance: Plague is one of three diseases still subject to International Health Regulations (IHR) quarantine provisions (along with cholera and yellow fever). Any suspected case requires immediate notification to national health authorities and the WHO. Pneumonic plague outbreaks require aggressive contact tracing and post-exposure prophylaxis.
Emergency Warning Signs
Plague is a medical emergency. Every hour of treatment delay increases mortality. Seek immediate emergency care if any of the following signs develop, particularly after exposure to rodent habitats or flea bites in endemic areas:
Immediate Life-Threatening Signs:
Rapidly enlarging, extremely painful lymph node (bubo) with high fever — suggestive of bubonic plague
Cough with bloody or watery sputum combined with fever — strongly suggestive of pneumonic plague, which is nearly 100% fatal if untreated and highly contagious
Bleeding from multiple sites (gums, nose, injection sites, skin purpura) — indicates DIC in septicemic plague
Blackening or gangrene of fingers, toes, nose, or ears — classic septicemic plague sign
Rapidly progressive hypotension and shock — septicemic plague with multi-organ failure
Respiratory distress — dyspnea, tachypnea, hypoxia progressing over hours
Critical Context for Suspicion:
Fever with painful lymphadenopathy in a person who has been in a plague-endemic area within the past 10 days
Rapidly fatal febrile illness with DIC in a previously healthy person
Severe pneumonia with bloody sputum and exposure history
Clinical Urgency:
Antibiotic treatment must be initiated within 24 hours of symptom onset to significantly reduce mortality
For pneumonic plague, treatment delays of even a few hours after symptom onset may be fatal
Do NOT wait for laboratory confirmation — treat empirically on clinical suspicion
Isolate suspected pneumonic plague patients immediately (droplet precautions plus contact precautions)
Notify public health authorities immediately — plague is a notifiable disease under IHR
Most common signs and symptoms
Symptom Presentation
Plague presents with distinct symptom patterns depending on the clinical form. All forms share an abrupt onset with rapid progression.
Bubonic Plague (80-95% of cases):
Sudden onset of high fever (38.5-41°C / 101-106°F) with chills and rigors
Bubo: Intensely painful, swollen lymph node (typically 2-10 cm), most commonly in the inguinal (groin) region (60-70%), followed by axillary (armpit) and cervical (neck) areas
The bubo develops near the site of the flea bite, usually within 2-8 days
Surrounding tissue is edematous and erythematous
Extreme malaise, prostration, and headache
Nausea, vomiting, and abdominal pain
If untreated, may progress to septicemic plague within 2-6 days
Septicemic Plague:
Can occur as primary septicemic plague (no bubo) or secondary to bubonic/pneumonic plague
High fever, chills, prostration, and rapid clinical deterioration
Disseminated intravascular coagulation (DIC): Bleeding from multiple sites, purpura, ecchymoses
Acral gangrene: Necrosis of fingers, toes, nose, and ears ("Black Death")
Hypotension and multi-organ failure
May present with abdominal pain mimicking an acute abdomen
Pneumonic Plague:
Most rapidly fatal form; can develop as primary (inhalation) or secondary (hematogenous spread)
Incubation as short as 1-3 days (sometimes hours for high-dose exposure)
Sudden onset of fever, malaise, and rapidly progressive cough
Watery then bloody sputum — highly infectious
Dyspnea, chest pain, and hemoptysis
Rapid progression to respiratory failure and death within 18-24 hours if untreated
Pharyngeal Plague (Rare):
Results from inhalation or ingestion of Y. pestis
Anterior cervical lymphadenopathy, pharyngitis
May be misdiagnosed as bacterial pharyngitis
Knowing the symptoms is the first step to a quick response.
Disease Course and Progression
Plague is characterized by rapid onset and fulminant progression, particularly in pneumonic and septicemic forms. Understanding the timeline is critical for clinical decision-making.
Bubonic Plague Timeline:
Exposure (Day 0): Infected flea bite, usually on lower extremities. The bite itself is often unnoticed.
Incubation (Days 1-8, typically 2-6): Y. pestis travels via lymphatics to the regional lymph node, where it multiplies rapidly, suppressing the innate immune response through its Type III secretion system.
Bubo Formation (Days 2-8): Sudden onset of painful, swollen lymph node (1-10 cm), most commonly inguinal. The patient develops high fever (38.5-41°C), chills, headache, and extreme malaise.
Progressive Phase (Days 3-7 without treatment): Worsening toxemia, potential bacteremia leading to secondary septicemic or pneumonic plague. The bubo may become fluctuant and suppurate.
Crisis (Days 5-10 without treatment): Septic shock, DIC, multi-organ failure, and death in 30-60% of untreated cases.
With Treatment: Clinical improvement typically begins within 24-72 hours. Bubo resolves over 1-3 weeks.
Pneumonic Plague Timeline (Most Rapid):
Exposure (Hour 0): Inhalation of respiratory droplets from an infected patient or animal, or secondary spread from bloodstream.
Incubation (1-3 days, sometimes hours): Bacteria rapidly multiply in pulmonary tissue.
Early Phase (Day 1-2): Fever, malaise, headache, body aches — initially nonspecific. Cough begins, initially non-productive.
Progressive Phase (Day 2-3): Rapidly worsening cough with watery then bloody sputum, dyspnea, chest pain. Patient becomes highly infectious.
Terminal Phase (Day 3-4 without treatment): Respiratory failure, cyanosis, hemodynamic collapse, and death. Without antibiotics, death occurs within 18-96 hours of symptom onset.
Septicemic Plague:
May present without antecedent bubo (primary septicemic) or progress from bubonic plague
Rapid onset of septic shock, DIC, purpura fulminans
Acral gangrene may develop within hours
Without treatment, nearly 100% fatal
How this disease is identified
Diagnosis
Plague diagnosis requires high clinical suspicion based on epidemiological context and rapid laboratory confirmation. Empiric treatment should never be delayed pending laboratory results.
Clinical Diagnosis: The combination of acute febrile illness with painful lymphadenopathy (bubo) in a patient with exposure to a plague-endemic area should prompt immediate empiric treatment. Pneumonic plague should be suspected in any patient with rapidly progressive febrile pneumonia with bloody sputum.
Laboratory Diagnostic Methods:
Culture (Gold Standard):
F1 Antigen Rapid Diagnostic Test (RDT):
PCR (Polymerase Chain Reaction):
Serology:
Specimen Collection:
Bubo aspirate: Inject 1 mL sterile saline into bubo, aspirate. High yield.
Blood cultures: Collect before antibiotics if possible, but do NOT delay treatment
Sputum: For suspected pneumonic plague
All specimens should be handled with appropriate biosafety precautions
Available treatment methods
Treatment and Management
Plague is treatable with prompt antibiotic therapy. The critical determinant of survival is the time from symptom onset to antibiotic initiation — ideally within 24 hours.
First-Line Antibiotics:
Gentamicin — 5 mg/kg IV/IM once daily (or 2 mg/kg loading then 1.7 mg/kg q8h)
Streptomycin — 1g IM twice daily (historical gold standard)
Alternative Antibiotics:
Doxycycline — 100 mg IV/PO twice daily
Ciprofloxacin — 400 mg IV q12h or 500-750 mg PO q12h
Levofloxacin — 500 mg IV/PO once daily
Chloramphenicol — Reserved for plague meningitis (good CNS penetration)
Supportive Care:
ICU admission for septicemic and pneumonic plague
Aggressive fluid resuscitation for septic shock
Management of DIC with blood products as needed
Mechanical ventilation for respiratory failure
Drainage of fluctuant buboes (only if indicated; do NOT incise non-fluctuant buboes)
Post-Exposure Prophylaxis:
Close contacts of pneumonic plague patients (within 2 meters) should receive 7 days of prophylactic doxycycline (100 mg PO q12h) or ciprofloxacin (500 mg PO q12h)
Active fever monitoring for 7 days after last exposure
Contacts who develop fever should be treated immediately
Infection Control:
Droplet precautions for suspected pneumonic plague (surgical mask, eye protection)
Standard precautions for bubonic plague
Isolate pneumonic plague patients in negative-pressure rooms if available
Most cases are effectively treated with early diagnosis.
How to protect yourself
Prevention Strategies
Plague prevention focuses on reducing human exposure to infected fleas and rodents, rapid detection of outbreaks, and post-exposure prophylaxis for contacts.
Personal Protective Measures:
Avoid contact with wild rodents (especially sick or dead animals) in endemic areas
Use insect repellent containing DEET on skin and permethrin on clothing to prevent flea bites
Do not handle wild rodent carcasses without gloves and appropriate PPE
Keep pets (especially cats) away from rodent habitats; use flea control on domestic animals. Cats are highly susceptible to plague and can transmit it to humans via respiratory droplets.
Protect food stores from rodent access; use sealed containers
Environmental and Community Measures:
Rodent-proof dwellings: Seal entry points, remove harborage (woodpiles, brush near buildings)
Environmental sanitation: Reduce rodent food sources (garbage management, grain storage)
Flea control before rodent control: Critically, flea treatment must precede rodent extermination campaigns, otherwise fleas from dying rodents will seek human hosts
Surveillance: Monitor rodent die-offs (epizootic events) as early warning signals
Vaccination:
No plague vaccine is currently commercially available for human use
A killed whole-cell vaccine was previously available but was discontinued due to limited efficacy and reactogenicity
Several next-generation vaccines (recombinant F1-V fusion protein) are in clinical trials
Vaccination does not protect against pneumonic plague
Post-Exposure Prophylaxis (PEP):
Doxycycline 100 mg PO twice daily for 7 days — for close contacts of pneumonic plague patients
Ciprofloxacin 500 mg PO twice daily for 7 days — alternative
TMP-SMX — alternative for children and pregnant women
Active fever monitoring for 7 days post-exposure
Close contacts include anyone within 2 meters of a pneumonic plague patient
Bioterrorism Preparedness: Y. pestis is classified as a CDC Category A bioterrorism agent. Preparedness plans include:
Stockpiling of antibiotics (doxycycline, ciprofloxacin) in the Strategic National Stockpile
Rapid diagnostic capacity at Laboratory Response Network (LRN) sites
Mass prophylaxis distribution plans
Preparation is the best protection.
Travel Advice
Plague risk for most travelers is very low, but certain activities and destinations warrant specific precautions.
Endemic Areas and Current Foci:
Madagascar: Highest global burden. Seasonal epidemics (September-April), including urban pneumonic plague outbreaks (e.g., 2017 epidemic: 2,348 cases, 202 deaths).
Democratic Republic of Congo: Persistent endemic foci in Ituri and Oriental provinces
Peru: Andean foothills, northern coastal regions
United States: Southwestern states (New Mexico, Arizona, Colorado, California) — average 7 cases/year
Other foci: Tanzania, Uganda, Myanmar, China (Yunnan, Qinghai), Bolivia, India (rare outbreaks)
Risk Activities:
Camping, hiking, or working in areas with rodent burrows
Handling or hunting wild rodents (prairie dogs, ground squirrels, marmots)
Visiting rural areas during known epizootic events (rodent die-offs)
Close contact with pneumonic plague patients (including healthcare workers)
Pre-Travel Recommendations:
During Travel:
Avoid contact with rodents and their burrows
Do not touch or approach sick or dead animals
Use insect repellent to prevent flea bites
Keep pets on flea prevention and away from wildlife
Sleep on elevated surfaces (not on the ground) in endemic areas
Post-Travel:
Seek immediate medical attention if fever, painful lymphadenopathy, or respiratory symptoms develop within 10 days of returning from an endemic area
Inform the clinician of travel history and potential plague exposure
Treatment delays can be fatal — do not wait for laboratory confirmation
Statistics and geographic data
Epidemiology
Plague is a re-emerging infectious disease with persistent natural foci on every inhabited continent except Australia. Despite its medieval reputation, plague remains a significant public health threat.
Global Burden:
WHO reports 1,000-3,000 cases annually worldwide (likely underreported)
Between 2010 and 2015: 3,248 cases and 584 deaths reported globally
Africa accounts for >90% of reported cases, primarily Madagascar and the DRC
Madagascar alone reports 200-700 cases annually, with periodic large epidemics
Geographic Distribution of Natural Foci:
Africa: Madagascar (largest burden), DRC, Tanzania, Uganda, Mozambique
Asia: Myanmar, China (Yunnan, Inner Mongolia, Qinghai), India (rare), Central Asian republics
Americas: Peru, Bolivia, Brazil, Ecuador; United States (southwestern states)
Europe: No active human foci, but rodent reservoirs persist in southeastern Russia/Central Asia
Notable Recent Outbreaks:
Madagascar 2017: 2,348 cases (pneumonic predominant), 202 deaths. Urban pneumonic plague in Antananarivo — unprecedented.
DRC 2006-2007: >1,000 suspected cases in Ituri Province
Colorado, USA 2014-2015: Small clusters linked to prairie dog exposure
China 2019-2020: Sporadic cases in Inner Mongolia associated with marmot hunting
Transmission Ecology:
Over 200 rodent species and 80 flea species can maintain Y. pestis
Sylvatic (wild) cycle: maintained in wild rodent populations (ground squirrels, gerbils, voles, marmots)
Urban cycle: Rattus rattus and Rattus norvegicus with Xenopsylla cheopis fleas
Epizootics (mass rodent die-offs) precede human epidemics as infected fleas seek new hosts
Climate factors: Plague incidence correlates with temperature (15-27°C optimal for flea reproduction) and rainfall patterns
Seasonality:
Madagascar: September-April (warm, rainy season)
United States: May-October
Asia: May-September
Outbreaks often follow periods of increased rodent abundance and subsequent epizootics
Who is most at risk
Risk Factors
Risk factors for plague infection relate primarily to exposure to infected fleas, rodents, or respiratory droplets from infected humans or animals.
Environmental and Behavioral Risk Factors:
Living in or visiting plague-endemic areas: Rural areas with active rodent reservoirs (Africa, Asia, Americas)
Contact with wild rodents: Hunting, skinning, handling, or residing near rodent burrows
Flea exposure: Presence of rodent fleas in domicile or peridomicile environment
Pet ownership in endemic areas: Cats are particularly dangerous — they develop plague pneumonia and can transmit directly to humans. Dogs are less susceptible but can carry infected fleas.
Outdoor sleeping: Sleeping on the ground or in structures without rodent-proofing
Occupational exposure: Farmers, herders, veterinarians, wildlife biologists, laboratory workers handling Y. pestis
Poor sanitation and housing: Inadequate rodent-proofing, proximity to garbage, peridomestic rodent infestations
Risk Factors for Pneumonic Plague Exposure:
Close contact (within 2 meters) with a patient with pneumonic plague
Healthcare workers caring for plague patients without appropriate PPE
Household contacts of pneumonic plague patients
Handling domestic cats with plague pneumonia
Risk Factors for Severe Disease:
Delay in seeking treatment: The single most important risk factor for death. Each hour of delay increases mortality.
Pneumonic or septicemic form: Inherently more lethal than bubonic plague
Age: Very young children and elderly are at higher risk of poor outcomes
Immunosuppression: HIV, organ transplant, immunosuppressive medications
Comorbidities: Diabetes, chronic lung disease, chronic liver disease
Limited healthcare access: Lack of diagnostic and antibiotic resources in rural endemic areas
Protective Factors:
Previous plague infection confers partial immunity (not absolute)
Consistent use of insect repellent and protective clothing in endemic areas
Prompt antibiotic treatment within 24 hours of symptom onset
Rodent and flea control in and around dwellings
Potential complications
Complications
Plague complications arise from the aggressive nature of Y. pestis infection and its capacity for rapid dissemination. Complications are most severe in septicemic and pneumonic forms.
Acute Systemic Complications:
Septic shock: Occurs in septicemic plague and as a complication of bubonic/pneumonic plague. Characterized by refractory hypotension, tachycardia, and multi-organ dysfunction. Mortality exceeds 50% even with intensive care.
Disseminated intravascular coagulation (DIC): A hallmark of septicemic plague. Results in simultaneous thrombosis and hemorrhage, with purpura fulminans, ecchymoses, and bleeding from mucosal surfaces.
Multi-organ failure: Kidney, liver, and respiratory failure commonly develop in septicemic plague. Dialysis and mechanical ventilation are frequently required.
Tissue and Organ-Specific Complications:
Peripheral gangrene: Ischemic necrosis of extremities (fingers, toes, nose, ears) due to DIC-related microvascular thrombosis. This is the origin of the name "Black Death." May require amputation in survivors.
Bubo suppuration and fistula: Untreated or late-treated buboes may suppurate, form fistulas, and drain spontaneously. Secondary bacterial infection of these sites is common.
Plague meningitis: Occurs in approximately 6% of plague cases, more common in children. Presents with headache, neck stiffness, and altered mental status. Requires chloramphenicol for adequate CNS penetration.
Acute respiratory distress syndrome (ARDS): Complicates pneumonic plague and secondary pneumonic spread from septicemic plague. High mortality even with ventilatory support.
Secondary Infections:
Nosocomial pneumonia in ventilated patients
Catheter-related bloodstream infections during prolonged ICU stays
Secondary bacterial infections of suppurating buboes
Long-Term Sequelae in Survivors:
Limb amputation: Required in survivors of septicemic plague with peripheral gangrene
Chronic lymphedema: May develop at sites of resolved buboes
Post-traumatic stress disorder: Common after severe plague illness
Renal impairment: Residual chronic kidney disease after acute kidney injury
Neurological sequelae: Persistent cognitive impairment and focal deficits in plague meningitis survivors
Public Health Complications:
Pneumonic plague outbreaks can cause community-wide panic and economic disruption
Healthcare system strain during urban outbreaks (Madagascar 2017)
International spread via air travel (port health surveillance is critical)
Expected outcomes and recovery
Prognosis and Outcomes
Plague prognosis is critically dependent on the clinical form, time to treatment initiation, and access to appropriate medical care.
With Prompt Antibiotic Treatment (within 24 hours):
Bubonic plague: CFR <5-10%. Most patients show clinical improvement within 48-72 hours. Bubo resolution may take 1-3 weeks.
Septicemic plague: CFR 20-40% even with treatment, due to rapid progression and multi-organ damage
Pneumonic plague: CFR 30-60% even with treatment if antibiotics are delayed beyond 18-24 hours from symptom onset; <5% with very early treatment
Without Treatment:
Bubonic plague: CFR 30-60%
Septicemic plague: CFR approaches 100%
Pneumonic plague: CFR 100% (virtually no survivors without antibiotics)
Recovery Timeline:
Fever typically resolves within 2-5 days of appropriate antibiotic therapy
Buboes may take 1-3 weeks to resolve; some require needle aspiration or surgical drainage
Full recovery from uncomplicated bubonic plague: 2-4 weeks
Septicemic plague survivors may require prolonged rehabilitation for organ damage and limb ischemia
Complications Affecting Prognosis:
DIC and multi-organ failure (septicemic form) carry the worst prognosis
Limb gangrene may require amputation in survivors
Meningitis (complicating ~6% of cases) requires specific treatment with chloramphenicol and carries higher morbidity
ARDS in pneumonic plague has high mortality even with ventilatory support
Predictors of Poor Outcome:
Delay in antibiotic treatment >24 hours from symptom onset
Pneumonic or septicemic presentation
Septic shock at presentation
Age extremes (very young and elderly)
Pre-existing immunosuppression
Development of DIC
The content on this page is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. If you have health concerns, consult a qualified healthcare professional. Medova is not a medical service provider.
Full terms of useKnow which vaccine you need? Great. Not sure? Just tell us your destination — we will figure it out and match you with a clinic. Free, no obligation.