Farm and Home Biosecurity
Consumer/General Public
Pneumonic Plague: Questions and Answers
What is plague?
Plague is an acute bacterial infection caused by the organism Yersinia
pestis (Y pestis). Millions of people in Europe died from plague in the
Middle Ages, when human homes and places of work were inhabited by flea-infested
rats. In the United States, the last urban plague epidemic occurred in Los
Angeles in 1924-25. Since then, human plague in the United States has occurred
as mostly scattered cases in rural areas (an average of 10 to 15 persons each
year).
What are the symptoms?
There are 5 forms of plague, all of which are uncommon and 3 of which are
very rare.
Usually, plague takes the form known as bubonic plague. The bacteria invade
the body and cause fever and lymph nodes to swell up (bubo) and become very
painful. The buboes can range in size from1-10cm in length.
Less frequently, the organism causes pneumonic plague, a form of pneumonia
with severe respiratory symptoms, rapidly developing cough and difficulty in
breathing. Pneumonic plague occurs when Y. pestis infects the lungs. The first
signs of illness in pneumonic plague are fever, headache, weakness, and cough
productive of bloody or watery sputum. The pneumonia progresses over 2 to 4 days
and may cause septic shock and, without early treatment, death.
The other very rare presentations of plague include meningitis, septicemic
and pharyngeal plague.
How do you catch plague?
Human plague most commonly occurs when plague-infected fleas bite humans who
then develop bubonic plague. The natural hosts are small animals such as wild
rats, ground squirrels, prairie dogs and other rodents. Man is an incidental
host.
Bubonic plague is generally not spread from person-to-person, except through
direct contact with any fluids from the swellings. Pneumonic plague can be
passed from person to person through the inhalation of droplets from the cough
or sneeze of an infected individual.
How long can you have the infection before developing symptoms?
The incubation period for plague is usually between 1 and 7 days. For plague
pneumonia following inhalation it is shorter at 1-4 days.
How can plague be prevented or treated?
Provided the disease is identified in its early stages, it can be treated
very effectively with antibiotics. Antibiotics can also be given to close
contacts of patients to help prevent them from developing the disease. Early
treatment of pneumonic plague is essential. Several antibiotics are effective,
including streptomycin, tetracycline, and chloramphenicol.
There is no vaccine against plague. The US-licensed formaldhyde-killed whole
bacilli vaccine was discontinued by its manufacturers in 1999 and is no longer
available. This killed vaccine demonstrated efficacy in preventing or
ameliorating bubonic disease, but does not prevent or ameliorate the development
of primary pneumonic plague.
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