Chapter 3Infectious Diseases Related To Travel

Kevin S. Griffith, Paul S. Mead

INFECTIOUS AGENT

Plague is caused by the 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 or dogs with plague, and rarely, contact with a pneumonic plague patient.

EPIDEMIOLOGY

Each year, 1,000–2,500 cases occur globally. Plague is endemic in 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 Mahajanga, Madagascar. All ages are at risk for infection; however, risk to travelers is largely restricted to rural endemic areas. Only 1 case associated with international travel has been reported in the United States in the past 2 decades.

CLINICAL PRESENTATION

The 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 3 clinical presentations of plague illness are as follows:

• Bubonic (more than 80%)—rapid onset of fever; painful, swollen, and tender lymph nodes, usually inguinal, axillary, or cervical
• Pneumonic—high fever, overwhelming pneumonia, cough, bloody sputum, chills
• Septicemic—fever, prostration, hemorrhagic or thrombotic phenomena, progressing to acral gangrene

DIAGNOSIS

Y. pestis can be isolated from bubo aspirates, blood cultures, or sputum culture if pneumonic. Diagnosis can be confirmed through culture rapid assays, available through public health laboratories, or serologic tests that show a 4-fold 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 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 can be used. Additional information can be found on the Division of Vector-Borne 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. 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. People working in health care settings should follow droplet precautions while working with suspected plague patients, especially if patient is coughing.

BIBLIOGRAPHY

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