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For further information, see CMDT Part 33-25: Plague

Key Features

Essentials of Diagnosis

  • History of exposure to rodents in endemic area

  • Sudden onset of high fever, muscular pains, and prostration

  • Axillary, cervical, or inguinal lymphadenitis (bubo)

  • Pustule or ulcer at inoculation site

  • Pneumonia or meningitis is often fatal

  • Positive smear and culture from bubo and positive blood culture

General Considerations

  • An zoonotic infection carried by wild rodents and caused by Yersinia pestis, a small bipolar-staining gram-negative rod

  • It is transmitted among rodents and to humans by the bites of fleas or from contact with infected animals

  • Following the flea bite, the organisms spread through the lymphatics to the lymph nodes, which become greatly enlarged (bubo). They may then reach the bloodstream to involve all organs

  • If pneumonia develops in a patient with plague, the infection can be transmitted by droplets to other individuals

  • The incubation period is 2–10 days

  • Because of its extreme virulence, its potential for dissemination and person-to-person transmission, and efforts to develop the organism as an agent of biowarfare, plague bacillus is considered a high-priority agent for bioterrorism


  • It is endemic in California, Arizona, Nevada, and New Mexico

  • Worldwide, Madagascar accounts for three-quarters of the global burden

Clinical Findings

Symptoms and Signs

  • The onset is sudden, with high fever, malaise, tachycardia, intense headache, delirium, and severe myalgias

  • A pustule or ulcer at the site of inoculation may be observed

  • Axillary, inguinal, or cervical lymph nodes become enlarged and tender and may suppurate and drain

  • Signs of meningitis may develop

  • With hematogenous spread, the patient may rapidly become toxic and comatose, with purpuric spots (black plague) appearing on the skin

  • Primary plague pneumonia is a fulminant pneumonitis with bloody, frothy sputum and sepsis

  • If pneumonia develops, tachypnea, productive cough, blood-tinged sputum, and cyanosis also occur

Differential Diagnosis

  • Lymphadenitis accompanying staphylococcal or streptococcal infections of an extremity

  • Sexually transmitted diseases, such as lymphogranuloma venereum or syphilis

  • Tularemia

  • Enteric or rickettsial fevers

  • Malaria

  • Influenza

  • Other bacterial pneumonias

  • Meningitis caused by other bacteria


Laboratory Tests

  • The plague bacillus may be found in Gram-stained smears from aspirates of buboes

  • Cultures from bubo aspirate or pus and blood are positive but may grow slowly

  • In convalescing patients, an antibody titer rise may be demonstrated by agglutination tests



  • Therapy should be started immediately once plague is suspected

  • Either streptomycin (the agent with which there is greatest experience), 1 g every 12 hours intravenously, or gentamicin, administered as a 2 mg/kg loading dose, then 1.7 mg/kg every 8 hours intravenously, is ...

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