Plague Information - Centers for Disease Control and Prevention

Frequently Asked Questions

What is plague?

Plague is a bacterial disease caused by Yersinia pestis. Wild rodents, especially ground squirrels and prairie dogs, are the natural reservoir for plague. Rats, wild rodents, cats, and dogs can become infected with plague and the disease is occasionally transmitted to people who are bitten by infected animals or infected fleas that feed on those animals.

Who gets plague?

Plague is extremely rare in the United States. A small number of cases (10-20) are reported each year in the United States, mainly in rural areas of the Southwest. Hunters and trappers have a greater chance of catching plague. Living in the Southwest and having a house dog or cat can also put people at risk.

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Are there different kinds of plague?

Yes. Only one bacterium causes plague but it can affect people in three different ways.

Bubonic plague gets its name from the enlarged and tender lymph glands, or nodes (called "buboes" during the 14th century, when the disease ravaged Europe). This is the most common form of plague.

Pneumonic plague is the most serious form and occurs when the plague bacteria infect the lungs.

Septicemic plague occurs when the bacteria multiply in the blood.

How is plague spread?

Bubonic plague and septicemic plague are transmitted primarily by the bite from infected fleas; however, transmission can occur by bites or scratches from infected wild rodents and cats, or contact with tissue from infected animals. Bubonic plague is rarely spread from person-to-person. Pneumonic plague occurs when a person inhales the plague bacteria. Pneumonic plague is far more contagious because it can be spread from person-to-person through the air by sneezing or coughing.

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What are the symptoms of plague?

Initial symptoms include fever, chills, muscle aches, headache, nausea, vomiting, diarrhea, abdominal pain, and extreme exhaustion. Swollen and tender lymph nodes near where the infected flea bit the person are typical of bubonic plague. Pneumonic plague usually presents with a cough, bloody sputum and difficulty breathing.

How soon after infection do symptoms appear?

The incubation period for both types of plague is 1 to 7 days after exposure to the bacteria.

How is plague diagnosed?

Health care workers can diagnose plague by doing laboratory tests on sputum, blood, spinal fluid, or infected lymph nodes. Individuals who present with acute onset of bloody sputum should be seen and evaluated by a medical provider as soon as possible so that appropriate treatment can begin.

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What is the treatment for plague?

Bubonic plague can be effectively treated with certain widely-available antibiotics, usually streptomycin or gentamicin. If untreated, it can become septicemic plague, and is fatal in approximately 50-60% of infected persons. Pneumonic plague is almost always fatal if not treated quickly after the onset of symptoms.

Does past infection with plague make a person immune?

Immunity after plague recovery is variable, and may not provide complete protection. There is no commercial plague vaccine available in the United States.

How can plague be prevented?

When traveling in areas where plague is common, it is important to avoid being bitten by infected fleas by using insecticides and repellants. Gloves should be worn when handling wildlife. Contact with rats, prairie dogs and other rodents should be avoided. Efforts should be made to control rodent and flea populations. Buildings should be rat-proofed, with appropriate storage and disposal of food, garbage, and refuse. Dogs and cats in such areas should be treated with insecticides to prevent flea infestation.

Patients with pneumonic plague should be quarantined until 3 full days of antibiotic treatment have been administered.

For more information, call the Vermont Department of Health, Epidemiology Field Unit, at 1-800-640-4374 (in VT only), or 1-802-863-7240.

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