Plague is a serious illness spread to humans by the bite of a flea carried by an infected animal, usually a wild rodent.
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The Black Death
In about 1300, a massive epidemic of a deadly disease known as plague began. The epidemic, sometimes called the Black Death, started in Asia, then spread westward from the Middle East to North Africa and Europe. Between 1347 and 1350, as many as 20 million people died from plague in Europe alone. Later waves of plague continued to sweep through Europe until about 1800. At the time, people were not sure what caused the disease. They blamed it on everything from the anger of God to unhealthy vapors given off by the sick or by swamps and cesspools.
What Is Plague?
In 1894, Alexandre Yersin, a French doctor studying plague in Hong Kong, first described the bacterium that causes plague. It is called Yersinia pestis after him. The bacteria are spread to humans by the bite of a flea carried by an infected animal, usually a wild rodent. Although plague is still a serious illness, it is now rare. During the 1980s, there was an average of 18 cases of plague a year in the United States. About one in seven of these patients died. There are sporadic outbreaks of plague each year worldwide. In the 1980s, outbreaks occurred in 17 countries, mostly in Africa, Asia, and South America.
Plague and Pestilence
The first well-known outbreak of plague, sometimes called the Plague of Justinian, occurred during the Roman Empire. The empire reportedly lost a quarter of its population to the disease. This outbreak struck Constantinople in 542, then spread into Western Europe. Later waves of plague continued to appear around the Mediterranean Sea for the next 200 years.
A second cycle of plague, known as the Black Death, had an even greater impact. This was the greatest medical disaster of the Middle Ages. In its first wave alone, from 1347 to 1350, plague killed about a quarter of Europe's population. Once again, waves of plague continued to come and go for hundreds of years. The results were
The U.S and the World
- There are about 1,000 to 2,000 cases of plague each year worldwide. Today, the disease is found in Asia, extreme southeastern Europe, Africa, North America, and South America.
- During the 1980s, there were out-breaks of plague in Africa, Asia, and South America.
- In the United States from 1970 to 1995, there were about 13 cases per year.
- There is no plague in Australia or most of Europe.
- Modern outbreaks of plague usually can be traced to house rats and their fleas. Such outbreaks still crop up in some developing countries. The last such outbreak in the United States occurred in Los Angeles in 1924-1925.
In North America, most cases of plague in the 1990s occurred in two regions: one in northern New Mexico, northern Arizona, and southern Colorado, and another in California, southern Oregon, and far western Nevada. In the southwestern states, rock squirrels and their fleas are the most common source of human plague. In the Pacific states, California ground squirrels and their fleas are the most common source. Other rodent sources include prairie dogs, wood rats, chipmunks, and other ground squirrels, and, less frequently, wild rabbits, and pet cats.
How Is Plague Spread?
Plague usually is spread from animal to animal and from animal to human by the bite of an infected flea. Less often, it is spread by direct contact with the body fluids or tissues of a sick or dead animal. For example, a person might catch plague while skinning an infected rabbit. Plague also can be spread by tiny droplets of bacteria that get into the air from the coughing of people or cats whose infection has spread to the lungs. Other people who breathe these droplets can catch plague.
People in the western United States who come into contact with animals that might carry plague run a risk of getting the disease. Such people include campers, hikers, and hunters who visit areas with animal plague; and pet owners and animal doctors who handle infected cats.
What Are the Symptoms?
There are three main types of plague: bubonic, septicemic, and pneumonic. Bubonic plague usually starts two to six days after a person comes into contact with plague bacteria. It leads to very tender, swollen lymph nodes * , called buboes, that are often hot to the touch. Other possible symptoms of bubonic plague include fever, chills, tiredness, head-ache, and an overall feeling of illness.
The disease can get worse quickly if treatment is not started right away. If bacteria invade the bloodstream, the result is a severe illness known as septicemic plague. Symptoms of septicemic plague include fever, chills, tiredness, stomach pain, bleeding into the skin and other organs, and shock (a sudden drop in blood flow throughout the body that can lead to physical collapse and death). If the infection spreads to the lungs, the result is a deadly illness known as pneumonic plague. Symptoms of pneumonic plague include fever, chills, coughing, trouble breathing, and shock. Without prompt treatment, most people with pneumonic plague soon die.
What Is the Treatment?
Early diagnosis and treatment can cut the death rate for plague to less than 5 percent. The doctor may suspect plague if a person develops the telltale symptoms and has been around wild rodents, wild rabbits, or sick or dead animals that eat rodents and rabbits. To be sure, the doctor can check for signs of plague bacteria in the person's blood, mucus that is coughed up, or lymph node samples.
Antibiotic drugs are given to fight the plague bacteria. In addition, people suspected of having pneumonic plague are kept away from others to keep from spreading the disease through coughing.
* lymph nodes are bean-sized round or oval masses of immune system tissue that store special cells that fight infection and other diseases. Clusters of them are found in the underarms, groin, neck, chest, and abdomen.
How Can It Be Prevented?
People who live, work, or play in areas with animal plague can take pre-cautions to reduce their risk, including:
- Getting rid of rodents in and around homes, workplaces, and campsites by removing brush, rock piles, junk, pet food, and food scraps from around such areas.
- Sealing rodent entry holes in buildings.
- Using flea sprays to kill fleas during outbreaks of animal plague.
- Not touching sick or dead rodents or rabbits.
- Reporting sick or dead rodents or rabbits that may have plague to the local health department.
A vaccine for plague is available. However, it is recommended only for people whose jobs place them at very high risk, such as those who work with plague bacteria in laboratories or with wild rodents in areas with plague. Travelers to countries reporting cases of plague, and people who may have come into contact with infected animals may be given antibiotics to help ward off the disease.
U.S. Centers for Disease Control and Prevention (CDC), Division of
Vector-Borne Infectious Diseases, 1600 Clifton Road N.E., Atlanta, GA
30333. CDC posts a fact sheet about plague at its website.