Facts about Plague


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Plague is caused by a bacteria called Yersinia pestis. It is transmitted to people through a flea bite or direct contact with an infected animal.

Fleas become infected by feeding on rodents, such as ground squirrels, chipmunks, prairie dogs, mice, rabbits and other mammals that are infected with the bacteria. Domestic dogs and cats can also contract plague by catching and eating infected rodents and rabbits or by being bitten by an infected flea. They may carry infected fleas home to their owners or, especially with cats, serve as a direct source of infection.

Plague has ravaged the world for centuries. Other names for the plague are “Black Death” and “the poor plague.” In the United State plague is commonly found in the southwestern states and it can be acquired at anytime during the year.

If left untreated, plague can have devastating effects. The bacteria invade the bloodstream and multiply, spreading rapidly throughout the body and causing a severe condition. About 14% (1 in 7) of all plague cases in the United States are fatal, with a 50-90% mortality rate if untreated.


From the time you are exposed to the disease to the time until symptoms appear is known as the incubation period. A person usually becomes ill with bubonic plague within two to six days after being infected.


Typically plague symptoms include sudden onset of fever and chills, severe headache, muscle aches, nausea, vomiting, extreme exhaustion, and a general feeling of overall illness.

There are three types of plague:

Bubonic: Bubonic plague symptoms also include extreme pain and swelling in lymph nodes draining the infection site. A swollen area is called a “bubo.” The most common form of plague is bubonic.

Septicemic: When bubonic plague goes untreated a severe blood infection (septicemia) occurs. Further symptoms may include abdominal pain, shock, and bleeding into the skin and other organs.

Pneumonic: Pneumonic plague involves the lungs and can be spread to another person by inhaling infected droplets expelled by coughing, from a person or animal, especially domestic cats, with pneumonic plague.

Septicemic and pneumonic forms of the disease are the most serious.


  • People living in rural or nonurban areas, especially in geographic areas with known plague.
  • People who have been in contact with sick animals, small rodents, or other possible hosts
  • People who have been participating in wilderness activities (eg: camping, hiking, sleeping on ground, hunting)
  • People who have recently been bitten by a flea
  • People who live in a community with recently confirmed plague activity.
  • People working with animals, such as veterinarian, veterinarian assistants or animal groomers

A person or animal suspected of having plague is immediately hospitalized and isolated to prevent the spread of the disease. Multiple laboratory tests will be conducted, and antibiotic treatment should begin as soon as possible. Individuals closely associated with the patient or exposed animal, particularly in the case of pneumonic plague should be placed under observation or given preventative antibiotic therapy, depending on the degree and timing of the contact.

If a plague patient does not receive antibiotic therapy, the disease can progress rapidly to death.

Although a plague vaccine does exist, it is not indicated for the general public.


The Mesa County Health Department monitors plague outbreaks through surveillance of human plague cases, and plague in rodents and other animals. In the event of an outbreak, the use of an effective insecticide to control rodent fleas may be used.

In cases when active animal plague is confirmed, closure of specific plague-infested campgrounds and restricted access to hazardous areas may be warranted.

The U.S. Public Health Services requires that all cases of suspected plague be reported immediately to local and state health departments and that the diagnosis is confirmed by the Centers for Disease Control and Prevention (CDC). As required by the International Health Regulations, CDC reports all U.S. plague cases to the World Health Organization.

Learn more about plague from CDC's Division of Vector-Borne Infectious Diseases Website:

  • Do not pick up or touch dead animals.
  • If plague has recently been found in your area, report any observations of sick or dead animals to the local health department or law enforcement officials.
  • Make your home rodent-proof. Eliminate sources of food and nesting places for rodents around homes, work places, and recreation areas; remove brush, rock piles, junk, cluttered firewood, and potential food supplies, such as pet and wild animal food.
  • If you anticipate being exposed to rodent fleas, apply insect repellents to clothing and skin, according to label instructions, to prevent flea bites. 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.
  • Treat rodent sites around your home with flea powder or a suitable insecticide.
  • Health authorities may use appropriate chemicals to kill fleas at selected sites during animal plague outbreaks.
  • Take your pet to a veterinarian if it becomes ill with a high fever and/or an abscess (open sore). Pets with plague can transmit the illness to humans.
  • See a physician if you become ill with a high fever and/or a swollen lymph node. Remember, plague is treatable.

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