Plague is a serious infectious disease that is common in rodents but is also transmissible to humans through the bite of rat fleas. Large worldwide epidemics have been recorded as early as the fourteenth century. Plague still occurs sporadically throughout the world.

The World Health Organization (WHO) considers plague one of the four most likely pathogens to be used in biological warfare (a state in which infectious agents or toxic chemicals are being used as a weapon of mass destruction).

What Causes Plague?

Plague is transmitted by fleas that have become infected with the Yersinia pestis germ from feeding on infected rodents such as rats, chipmunks, prairie dogs, ground squirrels, mice and other mammals. The disease is transmitted when an infected flea then feeds on humans. Plague is contagious in humans when an infected person has pneumonia and coughs infected saliva droplets in the air, which, in turn, are inhaled by a healthy person. The incubation period for plague is usually between two and six days following exposure to infected rodents or fleas.

How Is Plague Diagnosed?

Diagnosis of plague includes blood cultures to test for plague bacteria and microscopic examinations of the lymph glands, blood and sputum samples.

What Are the Symptoms of Plague?

The following are the most common symptoms of plague. However, each individual may experience symptoms differently. Symptoms may include:

  • Swollen and tender lymph glands with pain
  • Fever
  • Chills
  • Headache
  • Extreme exhaustion

The swollen gland is also called a "bubo," which gave rise to the term "bubonic plague." If left untreated, plague can enter the bloodstream and result in severe and often fatal pneumonia, with symptoms such as:

  • High fever
  • Chills
  • Cough
  • Difficulty breathing
  • Bloody sputum

The symptoms of plague may resemble other medical conditions or problems. Always consult your physician for a diagnosis.

How Is Plague Treated?

Specific treatment for plague will be determined by your physician based on:

  • Age, overall health and medical history
  • Extent of the condition
  • Your tolerance for specific medications, procedures or therapies

Treatment will include:

  • Hospitalization
  • Medical isolation
  • Antibiotic treatment (i.e., streptomycin, gentamicin, tetracyclines or chloramphenicol)

When left untreated, plague can result in rapid death. Approximately 14 percent of all plague cases in the U.S. each year are fatal.

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