An Introduction to Pneumonic Plague
Plague is an infectious disease that affects animals and humans. It is caused by the bacteria
Yersinia pestis, which are found in rodents and their fleas. Plague occurs in many areas of the world, including the United States.
Pneumonic plague occurs when
Yersinia pestis infects the lungs.
Pneumonic Plague: Understanding Yersinia Pestis
Yersinia pestis are Gram-negative bacteria. They are easily destroyed by sunlight and drying. Even so, when released into air, the bacteria will survive for up to one hour, although this could vary, depending on conditions.
Pneunomic Plague Compared to Other Types of Plague
Pneumonic plague is one of several forms of plague
(see Types of Plague). Depending on the circumstances, these forms of plague may occur separately or in combination.
Besides pneumonic plague, the other types of plague are:
How Is Pneunomic Plague Transmitted?
Pneumonic plague can spread from person to person through the air. Transmission can take place when someone breathes in aerosolized (gaseous) bacteria, as could happen in a bioterrorist attack. Pneumonic plague is also spread by breathing in Yersinia pestis that is suspended in respiratory droplets, from a person (or animal) with pneumonic plague. Becoming infected in this way, however, usually requires direct and close contact with the ill person or animal.
Pneumonic plague may also occur if a person with
bubonic or septicemic plague is untreated and the bacteria spread to the lungs.
Incubation Period for Pneunomic Plague
When a person becomes infected with the bacteria that cause pneumonic
plague, the bacteria begin to multiply within the lungs. After one to three days, symptoms of pneumonic plague can begin. The period between becoming infected and the start of
pneumonic plague symptoms is called the pneumonic
plague incubation period.
Symptoms of Pneunomic Plague
With pneumonic plague, the first signs of illness are:
- Fever
- Weakness
- Headache
- Rapidly developing pneumonia with:
o Shortness of breath
o Chest pain
o Cough
o Bloody or watery sputum (saliva and discharge from respiratory passages).
The pneumonia progresses for two to four days and may cause respiratory failure and shock. Death from pneumonic plague typically occurs within two to six days after symptoms begin. The mortality rate of pneumonic plague is 75 percent, despite appropriate
plague treatment.
Other than the lymphatic system, the lungs are the organ most commonly affected by
bubonic plague. Approximately 10 to 20 percent of people with
bubonic plague will develop pneumonic plague.
Diagnosing Pneunomic Plague
In order to make a pneumonic
plague diagnosis, the doctor will ask a number of questions and perform a physical exam. During the exam, the doctor will be looking at the skin and listening to the lungs for signs of disease. If the doctor has a high suspicion that a person has pneumonic plague, he or she will recommend certain tests.
Treating Pneunomic Plague
Early treatment of pneumonic plague is essential. If the doctor suspects pneumonic plague, treatment will be started even before the results of lab tests return. To reduce the chance of death, antibiotics must be given within 24 hours of the first symptoms of pneumonic plague. Streptomycin, gentamicin, the
tetracyclines, and chloramphenicol are all effective against pneumonic plague.
Antibiotic treatment for seven days should protect people who have had direct, close contact with infected patients. Wearing a close-fitting surgical mask may also protect against infection.
A plague vaccine is not currently available for use in the United States.
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