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Plague




Plague is an infectious disease caused by bacteria called Yersinia pestis. These bacteria are found mainly in rodents, particularly rats, and in the fleas that feed on them. Other animals and humans usually contract the bacteria from rodent or flea bites.

Historically, plague destroyed entire civilizations. In the 1300s, the "Black Death," as it was called, killed approximately one-third (20 to 30 million) of Europe's population. In the mid-1800s, it killed 12 million people in China. Today, thanks to better living conditions, antibiotics, and improved sanitation, current World Health Organization statistics show there were 2,118 cases in 2003 worldwide.

Transmission

Yersinia pestis is found in animals throughout the world, most commonly in rats but occasionally in other wild animals, such as prairie dogs. Most cases of human plague are caused by bites of infected animals or the infected fleas that feed on them. In almost all cases, only the pneumonic form of plague can be passed from person to person.

Forms of Plague

Y. pestis can affect people in three different ways: bubonic, septicemic, or pneumonic plague.

Bubonic Plague

In bubonic plague, the most common form, bacteria infect the lymph system and become inflamed. (The lymph or lymphatic system is a major component of your body's immune system. The organs within the lymphatic system are the tonsils, adenoids, spleen, and thymus.)

How is it contracted? Usually, bubonic plague is contracted by being bitten by an infected flea or rodent. In rare cases, Y. pestis bacteria, from a piece of contaminated clothing or other material used by a person with plague, enter through an opening in your skin.

What are the symptoms? Bubonic plague affects the lymph nodes (another part of the lymph system). Within three to seven days of exposure to the bacteria, flu-like symptoms will develop such as fever, headache, chills, weakness, and swollen, tender lymph glands (called buboes-hence the name bubonic).

Is it contagious? Bubonic plague is rarely spread from person to person.

Septicemic plague

This form of plague occurs when the bacteria multiply in the blood.

How is it contracted? Septicemic plague is contracted the same way as bubonic plague-usually through a flea or rodent bite. Septicemic plague also can appear as a complication of untreated bubonic or pneumonic plague.

What are the symptoms? Symptoms include fever, chills, weakness, abdominal pain, shock, and bleeding underneath the skin or other organs. Buboes, however, do not develop.

Is it contagious? Septicemic plague is rarely spread from person to person.



Pneumonic plague

This is the most serious form of plague and occurs when Y. pestis bacteria infect the lungs and cause pneumonia.

How is it contracted? Pneumonic plague can be contracted in one of two ways.
  • Primary pneumonic plague is contracted when plague is inhaled. This type of plague can be spread to someone else.
  • Secondary pneumonic plague develops when bubonic or septicemic plague goes untreated after the disease has spread to the lungs. At this point, the disease can be transmitted to someone else.
What are the symptoms? Within 1 to 3 days of exposure to airborne droplets of pneumonic plague, fever, headache, weakness, rapid onset of pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery sputum develop.

Is it contagious? Pneumonic plague is contagious. If someone has pneumonic plague and coughs, Y. pestis bacteria suspended in respiratory droplets is released into the air. An uninfected person can then develop pneumonic plague by breathing in those droplets.

Diagnosis

A health care provider can diagnosis plague by doing laboratory tests on blood or sputum or on fluid from a lymph node.

Symptoms Treatment

When the disease is suspected and diagnosed early, a health care provider can prescribe specific antibiotics, generally streptomycin or gentamycin as treatment options. Certain other antibiotics are also effective. Left untreated, bubonic plague bacteria can quickly multiply in the bloodstream, causing septicemic plague, or even progress to the lungs, causing pneumonic plague.



Prevention

Antibiotics
Health experts recommend antibiotics if you have been exposed to wild rodent fleas during a plague outbreak in animals, or to a possible plague-infected animal. Because there are so few cases of plague in the United States, experts do not recommend taking antibiotics unless its certain there has been exposure to plague-infected fleas or animals.

Vaccine
Currently, there is no commercially available vaccine against plague.

How Common Is Plague?

Approximately 10 to 20 people in the United States develop plague each year from flea or rodent bites-primarily from infected prairie dogs-in rural areas of the southwestern United States. About one in seven of those infected die from the disease. There has not been a case of person-to-person infection in the United States since 1924.

Worldwide, there have been small plague outbreaks in Asia, Africa, and South America.
Information obtained from National Institute of Health
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