Plague (PLAYG) is a potentially serious bacterial infection that is spread to humans by infected rodents and their fleas.
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What Is Plague?
Plague is a disease caused by the bacterium Yersinia pestis (yer-SIN-e-uh PES-tis). It has been in existence for at least 2,000 years and in the twenty-first century is still found in Africa, Asia, South America, and North America.
There are three types of plague. Pneumonic (nu-MOH-nik) involves the lungs; bubonic (byoo-BAH-nik), the most common form, involves the body's lymphatic system * ; and septicemic (sep-tih-SEE-mik) involves the bloodstream and spreads throughout the body. Septicemic plague can occur by itself or along with pneumonic or bubonic plague.
Wild rats and fleas often are associated with plague, because they were the primary carriers of the disease during history's most devastating outbreaks. Other types of rodents (and their fleas) can carry plague as well, such as prairie dogs, chipmunks, wood rats, and ground squirrels.
How Common Is Plague?
The World Health Organization reports 1,000 to 3,000 cases of plague worldwide annually. In the United States, 10 to 20 cases are reported every year, usually in rural areas in northern New Mexico, northern Arizona, southern Colorado, California, western Nevada, and southern Oregon. The last outbreak in the United States was in 1924-25 in Los Angeles. Plague has not been seen in Europe since World War II.
* lymphatic (lim-FAH-tik) system is a system that contains lymph nodes and a network of channels that carry fluid and cells of the immune system through the body.
Plague bacteria are considered to be one of several deadly organisms that could be used in biological warfare * . It is feared that the bacteria could be aerosolized (AIR-o-suh-lized), or processed into tiny particles that could be released into the air.
A plague vaccine * was available to the general public but was discontinued by its manufacturers in 1999. Even if the vaccine were made available today, it would not be able to prevent the pneumonic form of plague, which is resistant to treatment as well.
The plague has been used as a weapon before. In 1346 the Tartar army tried to capture the port city of Caffa on the Black Sea in the Crimea. The army catapulted bodies of plague victims over the city wall; an epidemic of plague ensued and the city surrendered.
* biological warfare is a method of waging war by using harmful microorganisms to purposely spread disease to many people.
* vaccine (vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.
The Black Death
The first pandemic (an outbreak of disease over a large geographical area, often worldwide) of plague chronicled by historians occurred between 542 and 546 A.D., during the Roman emperor Justinian's reign. The plague followed trade routes to other countries, and the Roman army itself carried plague during war campaigns throughout Asia Minor, Western Europe, Italy, and Africa. Outbreaks continued for the next 300 years before the disease finally subsided.
An equally devastating second pandemic erupted nearly 800 years later, as plague once again traveled across trade routes and infected population pockets throughout Europe. Known as the Black Death, this fourteenth century outbreak killed more than one third of Europe's population.
During these first two pandemics, the source of plague (rats and, more importantly, their infected fleas) was unknown. The spread of disease went unexplained, and many people feared it was a punishment sent by God.
How Is Plague Spread?
Plague is transmitted in several ways. The most common is from animal to human through the bite of infected fleas. Fleas living on infected animals ingest the animals' blood and the bacteria in it. They then spread the disease to other animals and humans through their bite, which can result in the bubonic or septicemic form of plague. Bacteria also can enter the body through an open cut or wound after direct contact with infected people or animals.
In addition, humans and animals (such as cats) with plague can spread the disease by releasing tiny drops containing the bacteria from their mouth and nose; in humans, this happens when a person coughs, sneezes, or talks. As these drops enter the air, the smaller ones can float for up to 1 hour, whereas the larger drops settle on nearby objects. A sneeze or cough can send thousands of infected particles into the air. If inhaled, these drops can cause the pneumonic form of plague. This way of spreading the disease requires relatively close contact with an infected person or animal.
What Are the Signs and Symptoms of Plague?
Symptoms typically appear 2 to 6 days after infection. Sudden fever, chills, and headache, followed by swollen, painful, hot-to-the-touch lymph nodes * , known as buboes (BYOO-boze), are the hallmarks of bubonic plague. Lymph nodes in the groin are most commonly affected. If left untreated, the infection eventually spreads to the bloodstream, causing sepsis * , pneumonia * , or meningitis * .
In septicemic plague, the bacteria multiply in the blood, causing symptoms such as fever, chills, weakness, abdominal * pain, nausea (NAW-zee-uh), and vomiting. As the infection progresses, the blood pressure drops and the blood is unable to clot * normally. The skin looks bruised from uncontrolled bleeding, which is why historically the disease was called the Black Death.
The pneumonic form of plague takes hold rapidly, with symptoms such as fever, cough, chills, chest pain, bloody sputum * , and headache. It can progress to respiratory failure * and shock * within 2 to 4 days.
How Do Doctors Diagnose and Treat Plague?
Determining whether a person was in close contact with animals that can carry plague or has traveled to an area where the plague is known to occur can be key in making the diagnosis. Bubonic plague can be identified by the characteristic swollen lymph nodes. A blood culture * and a lymph node biopsy * may be done, as well as a culture of a sputum sample to look for Yersinia pestis bacteria.
Getting timely treatment for plague is critical. Without treatment, bubonic plague is fatal in 50 to 60 percent of cases. Septicemic plague and pneumonic plague are fatal in almost all cases if not treated within 24 to 48 hours.
* lymph (LIMF) nodes are small, bean-shaped masses of tissue that contain immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* sepsis is a potentially serious spreading of infection, usually bacterial, through the bloodstream and body.
* pneumonia (nu-MO-nyah) is inflammation of the lung.
* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.
* abdominal (ab-DAH-mih-nul) refers to the area of the body below the ribs and above the hips that contains the stomach, intestines, and other organs.
* clot is the process by which the body forms a thickened mass of blood cells and protein to stop bleeding.
* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
* respiratory failure is a condition in which breathing and oxygen delivery to the body is dangerously altered. This may result from infection, nerve or muscle damage, poisoning, or other causes.
* shock is a serious condition in which blood pressure is very low and not enough blood flows to the body's organs and tissues. Untreated, shock may result in death.
Suspected plague patients are isolated and hospitalized, where they are treated with antibiotics, intravenous * (IV) fluids, and oxygen. Anyone who has come in close contact with someone diagnosed with plague is treated with antibiotics to prevent contracting the infection. All suspected cases of plague must be reported to state and local health departments. Treatment and full recovery from plague can take several weeks or longer. Complications of plague include damage to vital organs
How Can People Prevent Becoming Infected?
Some people are at a higher risk for developing plague than others, such as lab technicians who handle the bacterium or blood samples taken from people who are infected, people who work in areas where plague occurs, and people who work with animals that carry the disease.
A person's risk of developing plague can be lowered by limiting contact with wild animals that might carry the disease, removing potential food sources and shelter for rodents near the home, treating pet dogs and cats weekly for fleas, and using insecticides to kill fleas around the home during outbreaks of plague in wild animals. Rat management in rural and urban areas also can minimize the potential for disease.
Antibiotics sometimes are prescribed to prevent infection if a person has been exposed to plague.
* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.
* biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.
* intravenous (in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.
U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton
Road, Atlanta, GA 30333. The CDC is the U.S. government authority for
information about infectious and other diseases, including plague.
U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD
20894. The National Library of Medicine has a website packed with
information on diseases (such as plague) and drugs, consumer resources,
dictionaries and encyclopedias of medical terms, and directories of
doctors and helpful organizations.
World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27,
Switzerland. WHO provides information about plague at its website.