Author(s): David McCormick, Paul Mead

Infectious Agent

Yersinia pestis, the causative organism for plague, is a gram-negative coccobacillus.

Transmission

Y. pestis transmission usually occurs through the bite of infected rodent fleas. Less common exposures include handling infected animal tissues (e.g., among hunters and wildlife personnel); inhaling infectious droplets from cats or dogs with plague; and, rarely, contact with a patient who has pneumonic plague.

Epidemiology

Plague is endemic to rural areas in central and southern Africa, especially eastern Democratic Republic of the Congo, northwestern Uganda, and Madagascar; parts of the southwestern United States; the northeastern part of South America; central Asia; and the Indian subcontinent. The overall risk for travelers is low, and encountering Y. pestis while traveling is unlikely.

Although travelers’ risk is negligible (no plague cases have been reported among travelers returning to the United States in >40 years), cases of plague can lead to societal disruptions that complicate travel. For example, during a plague outbreak in India in the 1980s, planes from India were temporarily prevented from landing in Europe, although none of the passengers had symptoms of plague. In 2017, schools in the Republic of Seychelles were closed and large public gatherings banned in response to a plague outbreak in neighboring Madagascar.

Clinical Presentation

The incubation period is typically 1–6 days. Plague illness has 3 possible clinical presentations: bubonic (the most common), pneumonic, or septicemic. Clinical symptoms and signs of bubonic plague include rapid onset of fever and painful, swollen, and tender lymph nodes, usually axillary, cervical, or inguinal. Pharyngeal plague is rare and presents with fever, sore throat, and cervical lymphadenitis; in its early stages, it may be clinically indistinguishable from more common causes of pharyngitis. For pneumonic plague, signs and symptoms include high fever, overwhelming pneumonia, cough, bloody sputum, and chills. For septicemic plague, signs and symptoms include fever, prostration, and hemorrhagic or thrombotic phenomena, progressing to acral gangrene. Meningitis can also develop in up to 10% of patients with plague.

Diagnosis

Y. pestis can be isolated from bubo aspirates, blood cultures, or sputum culture if pneumonic. State public health laboratories or Centers for Disease Control and Prevention (CDC) laboratories can confirm diagnosis by culture or serologic tests for the Y. pestis F1 antigen. Plague is a nationally notifiable disease. For diagnostic support, clinicians can contact CDC’s Division of Vector-Borne Diseases (970-221-6400; dvbid@cdc.gov).

Treatment

Treatment for plague differs by clinical presentation and illness severity. Several different classes of antimicrobials effectively treat plague, but aminoglycosides and fluoroquinolones are considered first-line. Treating physicians can use doxycycline for bubonic or pharyngeal plague, but these should not be used for pneumonic or septicemic plague, or plague meningitis. If plague meningitis is suspected, use dual antibiotic therapy with chloramphenicol and a fluoroquinolone or aminoglycoside. For full treatment recommendations, see Antimicrobial Treatment and Prophylaxis of Plague: Recommendations for Naturally Acquired Infections and Bioterrorism Response.

Prevention

Travelers can prevent plague by reducing contact with fleas and potentially infected rodents and other wildlife. Although a live attenuated vaccine has been in use in Russia since the 1930s, no plague vaccine is currently available for commercial use in the United States or western Europe. A killed whole-cell vaccine was available in the United States for people with occupational risk, but this vaccine was discontinued in 1999. Australia continued to use this vaccine until 2005. Newer vaccines using a recombinant F1 antigen are in development, but none are commercially available or currently approved for use by the US Food and Drug Administration. Oral antibiotics, including doxycycline, ciprofloxacin, and levofloxacin can be prescribed for postexposure prophylaxis.

CDC website: Plague