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Map of Wyoming Plague Cases 1991-2010


What is Plague?

Plague is an infectious disease of animals and humans caused by a bacterium named Yersinia pestis.


How is plague transmitted?

Plague is transmitted by fleas that become infected with bacteria Yersinia pestis.


How do people get plague?

An individual can become infected with the plague bacteria due to the bite of a flea.


What is the basic transmission cycle?

Fleas become infected by feeding on rodents, such as the chipmunks, prairie dogs, ground squirrels, mice, and other mammals that are infected with the bacteria Yersinia pestis. Fleas transmit the plague bacteria to humans and other mammals during the feeding process. The plague bacteria are maintained in the blood systems of rodents.


Could you get plague from another person?

Yes, when an individual has plague, cough droplets containing the bacteria can often be expelled into the air and another person within arms reach is at risk of contracting the illness.


What are the signs and 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.


What is the incubation period for plague?

A person usually becomes ill with bubonic plague 2 to 6 days after being infected. When bubonic plague is left untreated, plague bacteria invade the bloodstream. When plague bacteria multiply in the bloodstream, they spread rapidly throughout the body and cause a severe and often fatal condition. Infection of the lungs with the plague bacterium causes the pneumonic form of plague, a severe respiratory illness. The infected person may experience high fever, chills, cough, and breathing difficulty, and expel bloody sputum. If plague patients are not given specific antibiotic therapy, the disease can progress quickly and result in death.


How many cases of plague occur in the U.S. and Wyoming?

Human plague in the United States has occurred as mostly scattered cases in rural areas (an average of 10 to 20 persons each year). Globally, the World Health Organization reports 1,000 to 3,000 cases of plague every year. Human plague is rare in Wyoming with 6 cases reported since 1978. 


How is plague treated?

According to experts, a patient diagnosed with suspected plague should be hospitalized and medically isolated. Laboratory tests should be performed, including blood cultures for plague bacteria and microscopic examination of lymph gland, blood, and sputum samples. Antibiotic treatment should begin as soon as possible after laboratory specimens are taken. Streptomycin is the antibiotic of choice. Gentamicin is used when streptomycin is not available. Tetracyclines and chloramphenicol are also effective. Persons who have been in close contact with a plague patient, particularly a patient with plague pneumonia, should be identified and evaluated. The U.S. Public Health Service requires that all cases of suspected plague be reported immediately to local and state health departments and confirmed by CDC officials. As required by the International Health Regulations, CDC reports all U.S. plague cases to the World Health Organization.


Is the disease seasonal in its occurrence?

No, plague can be acquired at anytime during the year.


Where is plague most common?

Generally, plague is most common in the southwestern states, particularly New Mexico and Arizona.


Who is at risk for getting 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.


Source: Centers for Disease Control and Prevention (CDC)