Paul S. Mead, Ingrid B. Weber

Infectious Agent

Plague is caused by gram-negative bacterium, Yersinia pestis.

Mode of Transmission

• Zoonotic disease is usually transmitted to humans by the bites of infected rodent fleas.
• Less common exposures include handling infected animal tissues (hunters, wildlife personnel); inhalation of infectious droplets from cats with plague; and, rarely, contact with a pneumonic plague patient.

Occurrence

• 1,000 to 2,000 cases occur globally each year.
• Rural areas in central and southern Africa, central Asia and the Indian subcontinent, the northeastern part of South America, and parts of the southwestern United States.
• Although rare, urban outbreaks of plague have been reported in Majunga, Madagascar.

Risk for Travelers

• All ages are at risk for infection; however, risk to travelers is largely restricted to rural endemic areas.
• Only one case associated with international travel has been reported in the United States in the past two decades.

Clinical Presentation

• Incubation period is typically 1–6 days.
• History is suggestive of exposure to rodents, rodent fleas, wild rabbits, sick or dead carnivores, or patients with pneumonic plague.
• Symptoms and signs of the three clinical presentations of plague illness include:
  • Bubonic (>80%)—rapid onset of fever; painful, swollen and tender lymph node, usually inguinal, axillary, or cervical
  • Pneumonic—high fever; overwhelming pneumonia; cough; bloody sputum; chills
  • Septicemic—prostration, hemorrhagic and/or thrombotic phenomena progressing to acral gangrene

Diagnosis

• Specimens: bubo aspirates; blood cultures; sputum culture if pneumonic
• Microscopic identification, culture confirmation; confirmatory and rapid assays available through public health laboratories
• Serologic tests: fourfold change in antibody titer to F1 antigen between acute- and convalescent-phase sera

Treatment

• Physicians should report all suspected plague cases to state or local health departments and/or consult with CDC to obtain information and access diagnostic services.
• Parenteral antibiotic therapy with streptomycin is the recommended first-line therapy; alternatively, gentamicin; or where treatment is limited to oral therapy, doxycycline.
• Additional information can be found on the Division of Vector-Borne Infectious Diseases website at www.cdc.gov/ncidod/dvbid/plague/index.htm.

Preventive Measures for Travelers

• No vaccine is currently available in the United States.
• Preventive measures are aimed at reducing contact with fleas and potentially infected rodents and other wildlife.
• Health-care workers should follow droplet precautions while working with suspected plague patients, especially if patient is coughing.
• Prophylactic antibiotic treatment is given only in the event of exposure to bites of wild rodent fleas during an outbreak, exposure to tissues of a plague-infected animal, or close exposure to another person or animal with suspected plague pneumonia.

References

1. Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a biological weapon: medical and public health management. Working Group on Civilian Biodefense. JAMA. 2000;283:2281–90.
2. Dennis DT, Campbell GL. Plague and other Yersinia infections. In: Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, Loscalzo J, editors. Harrison’s principles of internal medicine. 17th ed. New York: McGraw-Hill Medical Publishing Division; 2008. p. 980–6.
3. Gage KL. Plague. In: Collier L, editor. Microbiology and microbial infections. 9th ed. New York: Arnold; 1998.
4. Perry RD, Fetherston JD. Yersinia pestis—etiologic agent of plague. Clin Microbiol Rev. 1997;10(1):35–66.
5. CDC. Human plague—India, 1994. MMWR Morb Mortal Wkly Rep. 1994;43(38):689–91.
6. Boisier P, Rasolomaharo M, Ranaivoson G, et al. Urban epidemic of bubonic plague in Majunga, Madagascar: epidemiological aspects. Trop Med Int Health. 1997;2(5):422–7.
7. Boulanger LL, Ettestad P, Fogarty JD, et al. Gentamicin and tetracyclines for the treatment of human plague: review of 75 cases in New Mexico, 1985–1999. Clin Infect Dis. 2004;38(5):663–9.
8. CDC. Prevention of plague: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 1996;45(RR-14):1–15.
9. Kool JL. Risk of person-to-person transmission of pneumonic plague. Clin Infect Dis. 2005;40(8):1166–72.