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  • The plague is a severe, acute infection caused by Gram Negative bacillus, Yersinia pestis.
  • Two main forms are bubonic and pulmonic forms
  • Considered a Class A bioterrorism agent

Clinical Features

Bubonic plague

  • Eschar often forms at site of vector bite (usually flea bite)
  • Buboes (inflamed, necrotic or hemorrhagic lymph nodes) are pathognomonic
    • Usually in axilla or groin
  • Liver and splenic involvement
  • Septicemia
  • Death if untreated in 2-10 days

Pulmonic plague

  • Very contagious
  • Can be hematogenous or aerosolized (weapon form)
  • Hemoptysis
  • Mulilobar hemorrhagic pneumonia
  • Sepsis
  • Death if untreated in 48 hours

Differential Diagnosis

Lower Respiratory Zoonotic Infections

Bioterrorism Agents[1]

Category A

Category B

  • Ricin
  • Brucellosis
  • Epsilon toxin
  • Psittacosis
  • Q Fever
  • Staph enterotoxin B
  • Typhus
  • Glanders
  • Melioidosis
  • Food safety threats
  • Water safety threats
  • Viral encephalitis

Category C


Should be considered in any patient with clinical signs of plague and a recent history of travel to the western United States or any other plague endemic area.

Possible diagnostic samples:

  • Lymph node aspirate
    • Affected bubo should contain numerous organisms that can be evaluated microscopically and by culture.
  • Blood cultures
    • Organisms may be seen in blood smears if the patient is septicemic.
    • Blood smears taken from suspected bubonic plague patients early in the course of illness are usually negative for bacteria by microscopic examination but may be positive by culture.
  • Sputum
    • Culture is possible from sputum of very ill pneumonic patients
    • However, blood is usually culture-positive at this time as well.
  • Bronchial/tracheal washing
    • May be taken from suspected pneumonic plague patients
    • Not ideal for isolation of plague, since they often contain many other bacteria that can mask the presence of plague.

Gram, Wright, Giemsa, or Wayson's stained smears of peripheral blood, sputum, or lymph node specimen. Visualization of bipolar-staining, ovoid, Gram-negative organisms with a "safety pin" appearance permits a rapid presumptive diagnosis of plague.

  • If cultures yield negative results, and plague is still suspected, serologic testing is possible to confirm the diagnosis.
    • One serum specimen should be taken as early in the illness as possible, followed by a convalescent sample 4-6 weeks or more after disease onset.


Droplet precautions if pneumonic form suspected

  • Plague is a reportable disease to the CDC
  • If bioterrorism suspected, health authorities must be contacted immediately
  • Consult ID


Postexposure Prophylaxis

Active Disease


  • Admit
    • Droplet precautions if pneumonic form suspected

See Also


  1. Accessed 02/26/16