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Fact Sheet on Plague

Division of Epidemiology
275 E. Main St., Frankfort, KY  40621
(502) 564-3418 or 3261  
What is Plague?

Plague is the disease caused by the bacteria Yersinia pestis (Y pestis). There have been two great plague pandemics in the last 2000 years.  The first, starting in Egypt in AD 541, killed nearly 50 percent of the population.  The second pandemic earned the disease the nicknames ‘Black Death’ or the ‘Great Pestilence’, killing nearly one in three in Europe.

How is plague spread?

Fleas that have become infected with the Yersinia pestis bacteria transmit plague to humans and other mammals during the feeding process.  Direct contact with infected tissues or fluids from handling sick or dead animals can also spread the disease. Another mode of transmission can be respiratory droplets from rodents and humans with pneumonic plague.  Outbreaks in people occur in areas where housing and sanitation conditions are poor.  These outbreaks can occur in rural communities or in cities.  They are usually associated with infected rats and rat fleas that live in the home.

What are the symptoms of plague?

The typical sign of the most common form of human plague is a swollen and very tender lymph gland, accompanied by pain.  The swollen gland is called a “bubo” (hence the term “bubonic plague”).  Bubonic plague should be suspected when a person develops a swollen gland, fever, chills, headache and extreme exhaustion, and has a history of possible exposure to infected rodents, rabbits, or fleas. A person usually becomes ill with bubonic plague 2 to 6 days after being infected.  When bubonic plague is left untreated, the plague bacteria invade the bloodstream.  This condition is called septicemic plague and symptoms include fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organs.  The plague bacterium can also invade the lungs.  This is called pneumonic plague and is characterized by fever, chills, cough and difficulty breathing.  If plague patients are not given specific antibiotic therapy, the disease can progress rapidly to death.

How is plague diagnosed?

Material from the affected bubo should be taken whenever possible for diagnosis of bubonic plague.  Likewise, blood samples should be taken from suspected septicemic plague patients and bronchial/tracheal washing from suspected pneumonic plague patients.  These specimens are then tested for the presence of the Y pestis bacterium.

What is the treatment for plague?

Antibiotic treatment should begin as soon as possible after laboratory specimens are taken.  Prophylactic antibiotic treatment can protect persons who have had face-to-face contact with infected patients.

How can the plague be prevented?

In areas of known plague activity a combined approach using the following methods is recommended for risk reduction: environmental sanitation; educating the public on ways to prevent plague exposures; and preventive antibiotic therapy. 


Environmental Sanitation: It is important to remove food sources used by rodents and to make homes, buildings, warehouses, or feed sheds rodent-proof.  Consult professional pest management personnel for chemical control of fleas and rodents.  Following these simple tactics will reduce the risk of being bitten by infectious fleas of rodents and other animals in places where people live, work and recreate.

Public Health Education:  Report any plague activity in rodent populations; sick or dead animals should be brought to the attention of the local health department or law enforcement officials.  Eliminate food sources and nesting places for rodents.  Apply insect repellents to skin and clothing if you anticipate being exposed to rodent fleas.  Wear gloves when handling potentially infected animals.  If you live in areas where rodent plague occurs, treat pet dogs and cats for flea control regularly and do not allow these animals to roam freely.  Generally, plague is most common in the southwestern states, particularly New Mexico and Arizona.

Prophylactic antibiotics: Health authorities advise that antibiotics be given for a brief period to people who have been exposed to the bites of potentially infected rodent fleas (for example, during a plague outbreak) or who have handled an animal known to be infected with the plague bacterium.  Such experts also recommend that antibiotics be given if a person has had close exposure to a person or an animal (for example, a house cat) with suspected plague pneumonia.

For more information on plague visit the Center for Disease Control’s page at: 


Last Updated 5/17/2006