Plague is a disease caused by the bacterium Yersinia pestis. In its most common form, plague is also known as the bubonic plague. Buboes are the painful, swollen lymph nodes that are often found in people infected with Y. pestis. However, the bacterium can also cause disease in the lungs, the blood stream, and the central nervous system. These diseases are referred to as pneumonic plague, septicemic plague, and meningeal plague.

Y. pestis typically causes disease in rodents and other animals, but it can be spread to humans. If left untreated, plague is fatal 50 to 100 percent of the time depending on where the infection is found in the human body.

Plague is reportable to the Iowa Department of Public Health by Iowa Administrative Code 641 IAC 1.


Symptoms of plague typically begin within two to six days after a bite from an infected flea, or contact with an infected animal. These symptoms include:

  • Swollen, painful lymph nodes (called “buboes”)
  • Fever
  • Chills
  • Severe headache
  • Muscle aches
  • Nausea


Yersinia pestis is a bacterium that normally infects rodents such as rats, rock squirrels, wood rats, prairie dogs, and occasionally dogs and cats. It can be spread to humans in one of four main ways:

  • Flea bites. If an infected flea bites a human, that person may become infected.
  • Infected animals. Handling infected animals may lead to infection of a person. Infected animals in the United States are most commonly rodents, cats, and dogs.
  • Airborne. Breathing in airborne particles containing Y. pestis has been documented to cause disease.
  • Person-to-person. Close contact with an infected person can lead to spread of disease

Risk Factors

Every age group can be infected with Y. pestis. People who regularly handle animals that may be infected are at greater risk of contracting the disease. These people include:

  • Veterinarians and veterinary personnel
  • Hunters
  • Farmers
  • Anyone regularly in close contact with rodents or fleas


Prevention of plague mainly relies on the control of the flea and rodent populations. In areas where plague is commonly seen, flea control for dogs, cats, as well as the home or yard, will reduce the number of fleas that could spread the disease. A vaccine is available for laboratory workers or biologists working in areas where plague is commonly seen.


Plague can be treated with antibiotics. Early diagnosis and treatment is the key because some untreated forms of plague are often fatal.

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