Plague

Definition

Plague is a serious, potentially life-threatening infectious disease that is usually transmitted to humans by the bites of rodent fleas. It was one of the scourges of early human history. There are three major forms of the disease: bubonic, septicemic, and pneumonic.

Description

Plague has been responsible for three great world pandemics, which caused millions of deaths and significantly altered the course of history. A pandemic is a disease occurring in epidemic form throughout the entire population of a country, a people, or the world. Although the cause of the plague was not identified until the third pandemic in 1894, scientists are virtually certain that the first two pandemics were plague because a number of the survivors wrote about their experiences and described the symptoms.

The first great pandemic appeared in AD 542 and lasted for 60 years. It killed millions of citizens, particularly people living along the Mediterranean Sea. This sea was the busiest, coastal trade route at that time and connected what is now southern Europe, northern Africa, and parts of coastal Asia. This pandemic is sometimes referred to as the Plague of Justinian, named for the great emperor of Byzantium who was ruling at the beginning of the outbreak. According to the historian Procopius, this outbreak of plague killed 10,000 people per day at its height just within the city of Constantinople.

The second pandemic occurred during the fourteenth century, and was called the Black Death because its main symptom was the appearance of black patches (caused by bleeding) on the skin. It was also a subject found in many European paintings, drawings, plays, and writings of that time. The connections between large active trading ports, rats coming off the ships, and the severe outbreaks of the plague were understood by people at the time. This was the most severe of the three, beginning in the mid-1300s with an origin in central Asia and lasting for 400 years. Between a fourth and a third of the entire European population died within a few years after plague was first introduced. Some smaller villages and towns were completely wiped out.

The final pandemic began in northern China, reaching Canton and Hong Kong by 1894. From there, it spread to all continents, killing millions.

The great pandemics of the past occurred when wild rodents spread the disease to rats in cities, and then to humans when the rats died. Another route for infection came from rats coming off ships that had traveled from heavily infected areas. Generally, these were busy coastal or inland trade routes. Plague was introduced into the United States during this pandemic and it spread from the West towards the Midwest and became endemic in the Southwest of the United States.

About 10-15 Americans living in the southwestern United States contract plague each year during the spring and summer. The last rat-borne epidemic in the United States occurred in Los Angeles in 1924–25. Since then, all plague cases in this country have been sporadic, acquired from wild rodents or their fleas. Plague can also be acquired from ground squirrels and prairie dogs in parts of Arizona, New Mexico, California, Colorado, and Nevada. Around the world, there are between 1,000 and 2,000 cases of plague each year. Recent outbreaks in humans occurred in Africa, South America, and Southeast Asia.

Some people and/or animals with bubonic plague go on to develop pneumonia (pneumonic plague). This can spread to others via infected droplets during coughing or sneezing.

Plague is one of three diseases still subject to international health regulations. These rules require that all confirmed cases be reported to the World Health Organization (WHO) within 24 hours of diagnosis. According to the regulations, passengers on an international voyage who have been to an area where there is an epidemic of pneumonic plague must be placed in isolation for six days before being allowed to leave.

While plague is found in several countries, there is little risk to United States travelers within endemic areas (limited locales where a disease is known to be present) if they restrict their travel to urban areas with modern hotel accommodations.

Over the past few years, this infection primarily of antiquity has become a modern issue. This change has occurred because of the concerns about the use of plague as a weapon of biological warfare or terrorism (bioterrorism). Along with anthrax and smallpox, plague is considered to be a significant risk. In this scenario, the primary manifestation is likely to be pneumonic plague transmitted by clandestine aerosols. It has been reported that during World War II the Japanese dropped "bombs" containing plague-infected fleas in China as a form of biowarfare.

Causes and symptoms

Fleas carry the bacterium Yersinia pestis, formerly known as Pasteurella pestis. The plague bacillus can be stained with Giemsa stain and typically looks like a safety pin under the microscope. When a flea bites an infected rodent, it swallows the plague bacteria. The bacteria are passed on when the fleas, in turn, bite a human. Interestingly, the plague bacterium grows in the gullet of the flea, obstructing it and not allowing the flea to eat. Transmission occurs during abortive feeding with regurgitation of bacteria into the feeding site. Humans also may become infected if they have a break or cut in the skin and come in direct contact with body fluids or tissues of infected animals.

More than 100 species of fleas have been reported to be naturally infected with plague; in the western United States, the most common source of plague is the golden-manteled ground squirrel flea. Chipmunks and prairie dogs have also been identified as hosts of infected fleas.

Since 1924, there have been no documented cases in the United States of human-to-human spread of plague from droplets. All but one of the few pneumonic cases have been associated with handling infected cats. While dogs and cats can become infected, dogs rarely show signs of illness and are not believed to spread disease to humans. However, plague has been spread from infected coyotes (wild dogs) to humans. In parts of central Asia, gerbils have been identified as the source of cases of bubonic plague in humans.

Bubonic plague

Two to five days after infection, patients experience a sudden fever, chills, seizures, and severe headaches, followed by the appearance of swellings or "buboes" in armpits, groin, and neck. The most commonly affected sites are the lymph glands near the site of the first infection. As the bacteria multiply in the glands, the lymph node becomes swollen. As the nodes collect fluid, they become extremely tender. Occasionally, the bacteria will cause an ulcer at the point of the first infection.

Septicemic plague

Bacteria that invade the bloodstream directly (without involving the lymph nodes) cause septicemic plague. (Bubonic plague also can progress to septicemic plague if not treated appropriately.) Septicemic plague that does not involve the lymph glands is particularly dangerous because it can be hard to diagnose the disease. The bacteria usually spread to other sites, including the liver, kidneys, spleen, lungs, and sometimes the eyes, or the lining of the brain. Symptoms include fever, chills, prostration, abdominal pain, shock, and bleeding into the skin and organs.

Pneumonic plague

Pneumonic plague may occur as a direct infection (primary) or as a result of untreated bubonic or septicemic plague (secondary). Primary pneumonic plague is caused by inhaling infective drops from another person or animal with pneumonic plague. Symptoms, which appear within one to three days after infection, include a severe, overwhelming pneumonia, with shortness of breath, high fever, and blood in the phlegm. If untreated, half the patients will die; if blood poisoning occurs as an early complication, patients may die even before the buboes appear.

Life-threatening complications of plague include shock, high fever, problems with blood clotting, and convulsions.

Diagnosis

Plague should be suspected if there are painful buboes, fever, exhaustion, and a history of possible exposure to rodents, rabbits, or fleas in the West or Southwest. The patient should be isolated. Chest x rays are taken, as well as blood cultures, antigen testing, and examination of lymph node specimens. Blood cultures should be taken 30 minutes apart, before treatment.

A group of German researchers reported in 2004 on a standardized enzyme-linked immunosorbent assay (ELISA) kit for the rapid diagnosis of plague. The test kit was developed by the German military and has a high degree of accuracy as well as speed in identifying the plague bacillus. The kit could be useful in the event of a bioterrorist attack as well as in countries without advanced microbiology laboratories.

Treatment

As soon as plague is suspected, the patient should be isolated, and local and state departments notified. Drug treatment reduces the risk of death to less than 5%. The preferred treatment is streptomycin administered as soon as possible. Alternatives include gentamicin, chloramphenicol, tetracycline, or trimethoprim/sulfamethoxazole.

Prognosis

Plague can be treated successfully if it is caught early; the mortality rate for treated disease is 1-15% but 40-60% in untreated cases. Untreated pneumonic plague is almost always fatal, however, and the chances of survival are very low unless specific antibiotic treatment is started within 15-18 hours after symptoms appear. The presence of plague bacteria in a blood smear is a grave sign and indicates septicemic plague. Septicemic plague has a mortality rate of 40% in treated cases and 100% in untreated cases.

Prevention

Anyone who has come in contact with a plague pneumonia victim should be given antibiotics, since untreated pneumonic plague patients can pass on their illness to close contacts throughout the course of the illness. All plague patients should be isolated for 48 hours after antibiotic treatment begins. Pneumonic plague patients should be completely isolated until sputum cultures show no sign of infection.

Residents of areas where plague is found should keep rodents out of their homes. Anyone working in a rodent-infested area should wear insect repellent on skin and clothing. Pets can be treated with insecticidal dust and kept indoors. Handling sick or dead animals (especially rodents and cats) should be avoided.

Plague vaccines have been used with varying effectiveness since the late nineteenth century. Experts believe that vaccination lowers the chance of infection and the severity of the disease. However, the effectiveness of the vaccine against pneumonic plague is not clearly known.

Vaccinations against plague are not required to enter any country. Because immunization requires multiple doses over a 6-10 month period, plague vaccine is not recommended for quick protection during outbreaks. Moreover, its unpleasant side effects make it a poor choice unless there is a substantial long-term risk of infection. The safety of the vaccine for those under age 18 has not been established. Pregnant women should not be vaccinated unless the need for protection is greater than the risk to the unborn child. Even those who receive the vaccine may not be completely protected. The inadequacy of the vaccines available as of the early 2000s explains why it is important to protect against rodents, fleas, and people with plague. A team of researchers in the United Kingdom reported in the summer of 2004 that an injected subunit vaccine is likely to offer the best protection against both bubonic and pneumonic forms of plague.

KEY TERMS

Bioterrorism— The use of disease agents to terrorize or intimidate a civilian population.

Buboes— Smooth, oval, reddened, and very painful swellings in the armpits, groin, or neck that occur as a result of infection with the plague.

Endemic— A disease that occurs naturally in a geographic area or population group.

Epidemic— A disease that occurs throughout part of the population of a country.

Pandemic— A disease that occurs throughout a regional group, the population of a country, or the world.

Septicemia— The medical term for blood poisoning, in which bacteria have invaded the bloodstream and circulates throughout the body.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Plague (Bubonic Plague; Pestis; Black Death)." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Davis, S., M. Begon, L. DeBruyn, et al. "Predictive Thresholds for Plague in Kazakhstan." Science 304 (April 30, 2004): 736-738.

Gani, R., and S. Leach. "Epidemiologic Determinants for Modeling Pneumonic Plague Outbreaks." Emerging Infectious Diseases 10 (April 2004): 608-614.

Splettstoesser, W. D., L. Rahalison, R. Grunow, et al. "Evaluation of a Standardized F1 Capsular Antigen Capture ELISA Test Kit for the Rapid Diagnosis of Plague." FEMS Immunology and Medical Microbiology 41 (June 1, 2004): 149-155.

Titball, R. W., and E. D. Williamson. "Yersinia pestis (Plague) Vaccines." Expert Opinion on Biological Therapy 4 (June 2004): 965-973.

Velendzas, Demetres, MD, and Susan Dufel, MD. "Plague." eMedicine December 2, 2004. 〈http://www.emedicine.com/EMERG/topic428.htm〉.

ORGANIZATIONS

Centers for Disease Control. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. 〈http://www.cdc.gov〉.

National Institute of Allergies and Infectious Diseases, Division of Microbiology and Infectious Diseases. Bldg. 31, Rm. 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892.

World Health Organization. Division of Emerging and Other Communicable Diseases Surveillance and Control. 1211 Geneva 27, Switzerland.

OTHER

Bacterial Diseases (Healthtouch). 〈http://www.healthtouch.com/level1/leaflets/105825/105826.htm〉.

Bug Bytes. 〈http://www.isumc.edu/bugbytes/〉.

Centers for Disease Control. 〈http://www.cdc.gov/travel/travel.html〉.

Infectious Diseases Weblink. 〈http://pages.prodigy.net/pdeziel/〉.

International Society of Travel Medicine. 〈http://www.istm.org〉.

World Health Organization. 〈http://www.who.ch/〉.

PLAGUE

PLAGUE. The first great plague pandemic (1347–1350) was the greatest single epidemic interval in European history, yet some of the plagues of the period from 1500 to 1750 witnessed catastrophic mortality, in some cases over 40 percent. However, there was no continent-wide plague during any three-year interval after the Black Death of the fourteenth century. While in particular times and places later epidemics were as great as those of the Black Death, the burdens of mortality and disruption to ordinary life events fell most heavily upon those who could not escape to safe locales. Privileged sectors of the population typically had choices among fairly reliable strategies for avoiding exposure to plague.

The losses and costs of great epidemics between 1500 and 1750 can often be documented because one of the strategies of the elite and of governments representing them was to create surveillance systems that monitored urban mortality. After the invention of printing, local histories of plagues and plague treatises magnified the activities of urban administrators during mortality crises, reinforcing reams of correspondence and other non-printed records of church and state actions to minimize social and economic disruption from plague. In general, Italy and Spain led the rest of Europe in monitoring disease threats, relying upon trade and travel restrictions, urban boards of health, and hospital isolation strategies to segregate the ill from the well. All of these measures expanded bureaucratic surveillance and record keeping, and provided those with access to information a way to minimize the social and economic costs of plague. Collective governmental responses were more readily adopted in regions that remained Catholic. Protestants, instead, tended to encourage individual charitable care of one's afflicted neighbors, while retaining a strong sense that plague occurred as the result of God's moral judgment on the sinful. Therefore, fleeing the plague, as one would flee sin, was also sanctioned. Because plague controls were bureaucratized in what became the Catholic countries, better documentation of plague losses and responses survives from the late Middle Ages. Protestant regions began parish-level registration of births, marriages, and deaths after Catholic reforms at the Council of Trent (1545–1563). Such records were created to reinforce the sense of community and responsibility among members of individual Protestant churches, but historical demographers have used them in modern times to provide documentation of mortality crises comparable to urban mortality registers.

The cause or causes of these recurrent epidemics is the subject of considerable recent debate. Most geographical, demographical, and epidemiological evidence available from rural continental Europe suggests a slow spread of human mortality across trade and travel routes, patterns consistent with a rodent-borne bubonic plague. Great urban regions were served, however, by interregional trade, maritime and riverine, and were centers for distribution of infectious diseases. The practice of confining the ill and the well together in their homes or in vast pesthouses fueled morbidity and mortality during times of plague. The lazaretto of Milan, for example, held 12,000 to 15,000 people daily over the worst month of the murderous 1630 epidemic, in a complex that had a total of 256 enclosed rooms and minimal provision of clean water and medical care.

Recurrent plagues caused local population losses far steeper than chronic warfare or the burdens of other diseases. In the 150 years following the Black Death pandemic, the overall population of Europe fell 30 to 50 percent. Depopulation was especially dramatic in rural areas that had been cultivated during the High Middle Ages, leaving visible aerial traces of "deserted villages" and once-farmed land. As the overall population of Europe fell after the Black Death, the political and economic management of rural areas shifted to urban landowners, typically maximizing profits by turning the uses of the land to labor-conserving tasks, such as sheepherding (in Britain) or cattle-farming (in German and eastern European regions). European population recovery in the sixteenth century still left cities unable to replace their numbers, even in non-plague years. Cities had to draw their labor forces from the countryside. Rural to urban migration fueled early urban industries, such as cloth manufacture. Mountainous regions exploited mining. The first 150 years of recurrent plagues in Europe intersected with the beginnings of print, guns, and global trade all orchestrated from urban monetary sources of power, all requiring the move from agriculture to industry.

The economic costs of plagues in towns and cities increased over the early modern centuries, in part because of surveillance and isolation practices, in part because destruction of personal property dramatically impoverished survivors. Urban health boards devised mechanisms for sealing personal property within homes when early cases of plague were identified. With the seal unbroken, a closet or room could escape the fires and acids of disinfection procedures if plague subsequently entered the household. Maritime states meanwhile created the first international health procedures, codifying lengths of detention of people and goods in quarantine, mechanisms for disinfecting cargo, and the symbolism of a yellow flag, to indicate a ship that had "touched" plague.

Whatever the causes or the demographic and economic effects of recurrent plague, the methods of controlling both exposure to plague elsewhere and the unacceptable consequences of an epidemic locally established a tradition in epidemic management that is still very much a part of Western society. From particular urban plagues there also survives a legacy of literary and artistic production, of which Daniel Defoe's 1722 A Journal of the Plague Year, about the 1665 Great Plague in London, and Alessandro Manzoni's 1827 I promessi sposi (The betrothed), set in seventeenth-century Italy, are the two best-known novels. Plague art typically focused on divine retribution for sin, and the intervention of saints (especially St. Roch and St. Sebastian) to aid the plague-stricken, collective penance, and votive gifts expressing communal thanks for a specific plague's ending were popular themes. By the seventeenth century, plague art often portrayed themes of religious devotion to the sick even amid a chaotic tableau of suffering.

Plague, whatever its cause or causes, receded from Europe during the reign of Louis XIV (1643–1715). The last plagues in northern Europe and Britain occurred in the 1660s; the last plague in southern Europe occurred in Marseilles in 1720–1721. Messina, in Sicily, was stricken in 1743 and during the later eighteenth century the Austro-Hungarian Empire devised an extraordinary thousand-mile-long cordon sanitaire, a military border between Christian Europe and Muslim regions to the east. Whether through such aggressive measures to minimize all contact with plague in the Middle East and southern Russia, or because maritime trade was increasingly directed over the North Atlantic, commerce with regions that still experienced plague declined steeply. Local commercial barriers to the importation of plague certainly played a role in the plague's disappearance. But so, too, did the widespread use of arsenic oxide, a colorless, tasteless rat poison, by the late seventeenth century. Some have further speculated that the disappearance of plague in the years from 1650 to 1750 may have been the result of global ecological changes, reflected in the cooler climate called the "Little Ice Age" and the absence of sunspot activity called the "Maunder Minimum." The disappearance of plague, whatever its cause or causes, did coincide with the beginning of the modern rise of population throughout Eurasia and European domination of overseas trade.

See also Public Health .

BIBLIOGRAPHY

Appleby, Andrew. "The Disappearance of Plague: A Continuing Puzzle." The Economic History Review, ser. 2, 33 (1980): 161–173.

Boeckl, Christine M. Images of Plague and Pestilence: Iconography and Iconology. Sixteenth Century Essays and Studies, vol. 53. Kirksville, Mo., 2000.

Cipolla, Carlo. Public Health and the Medical Profession in the Renaissance. Cambridge, U.K., and New York, 1976.

Jones, Colin. "Plague and Its Metaphors in Early Modern France." Representations 53 (1996): 97–127.

Konkola, Kari. "More than a Coincidence? The Arrival of Arsenic and the Disappearance of Plague in Early Modern Europe." Journal of the History of Medicine and Allied Sciences 47 (1992): 186–209.

Rothenberg, Gunther E. "The Austrian Sanitary Cordon and the Control of the Bubonic Plague, 1710–1871." Journal of the History of Medicine and Allied Sciences 28 (1973): 15–23.

Slack, Paul. The Impact of Plague in Tudor and Stuart England. London and Boston, 1985.

Ann Carmichael

Plague

For centuries past, plague was the scourge of the earth, killing at least an estimated 163 million people during three major worldwide pandemics. Today, plague still exists in the world although the number of cases and deaths is much lower. Plague still infects several thousand people a year and kills several hundred. Most cases are in southern Africa, Asia, and central South America.

Plague is an infectious disease that affects animals and humans. It is caused by the bacterium Yersinia pestis and is usually found in rodents and their fleas. When released into the air, the bacterium can survive for up to an hour. People usually contract the disease after being bitten by an infected flea or after handling an infected animal. To reduce the risk of death, antibiotics must be given within 24 hours after the first symptoms occur.

There are three types of plague and they can occur separately or in combination. The types are:

• Bubonic plague, the most common form of the disease. It does not spread from person to person but is transmitted when an infected flea bites a person or when material contaminated with the bacterium enters through a cut in a person's skin. Symptoms include swollen lymph glands, fever, headache, chills, and weakness.
• Pneumonic plague, which infects a person through the lungs. It can be spread in the air from person to person. Symptoms include fever, headache, weakness, shortness of breath, chest pain, cough, and pneumonia.
• Septicemic plague, which occur when plague bacteria multiply in the blood. It can occur by itself or be a complication of pneumonic or bubonic plague. It is not spread from person to person. Symptoms include fever, chills, exhaustion, abdominal pain, shock, and bleeding into the skin and other organs.

To reduce the chance of death, people with plague must receive antibiotics within 24 hours after the first symptoms appear. Effective antibiotics include streptomycin, gentamicin, and tetracycline. Early treatment allows most people with plague to be cured if diagnosed in time. There is no vaccine against plague available.

From 1954 to 1997, there were 80,613 reported plague cases in 38 countries, of which 6,587 people died, according to the World Health Organization (WHO). The highest number of cases, 6,004, occurred in 1967, and the lowest number, 200, occurred in 1981. These numbers likely represent only about a third of the actual number of cases, due to inadequate surveillance and reporting methods, according to WHO.

Plague has been around since the dawn of civilization and probably existed in animals before humans inhabited the earth. The first recorded plague epidemic occurred in 1320 BC and is described by its symptoms in the Bible (I Samuel, V and VI). It is not known how many people were infected. The first known pandemic, or severe worldwide epidemic, occurred in Asia, Africa, and Europe between 542 and 546 AD. It was named Justinian's plague, after the emperor of the Byzantine Empire at the time, and killed an estimated 50 million to 100 million people.

The first pandemic is believed to have started in Egypt, spreading north through the eastern Mediterranean. The plague struck at a critical time. In Constantinople, the capital of the Byzantine empire, Justinian and his generals were in the midst of battles to rejoin Byzantium to the remains of Western Roman Empire. Justinian's dream was to reestablish the former Roman Empire; and he might have succeeded if not for the plague. Procopius, a historian living in Constantinople at the time, vividly described the plague and its effects. His writings also include an accurate description of what would later be called the bubonic plague. He wrote about agitated, feverish disease victims with painfully enlarged lymph nodes (buboes) under their arms and in their groins. According to Procopius, 300,000 people died within the city alone. It is impossible to verify whether that figure is accurate, but it is certain that the plague had a dramatic effect on history. Justinian's plans to re-establish the Roman Empire were very likely derailed because of the loss of manpower. In the west, the remnants of the Western Roman Empire collapsed into the Dark Ages.

Following the initial outbreak in 542, the plague disappeared and reappeared at intervals over the next 200 years. The years 542 to 600 were the most intense plagues years, but local epidemics flared up throughout the Mediterranean region through the mid-eighth century. The population of Europe wasn't able to recover between outbreaks and some historians estimate that the population dropped by half between 542 and 700. After the late-eighth century, plague disappeared from Europe for nearly 600 years.

The second pandemic is the infamous "Black Death" from 1347 to 1350 AD.It killed from 25 million to 50 million people, half in Asia and Africa and half in Europe (a quarter of the population). Its entry into Europe was through Kaffa, a small Italian trading colony on the shore of the Black Sea in Crimea. Kaffa was besieged by an army and during the siege, plague broke out among the soldiers. According to some sources, the soldiers threw the corpses of those who died over the town walls to spread plague among the men defending the town. Whether that caused plague to break out in the town is unknown, but the defenders were afflicted. They managed to get to their boats and flee to Italy, unknowingly carrying the disease with them.

By late 1347, plague was widespread in the Mediterranean region, and in 1348 it spread throughout Italy, France, and England. The Middle East and the Far East were also severely affected. Medieval physicians were at a loss to explain the disease. Some claimed it was due to person-to-person infection, while others said it arose from a poisonous atmosphere . Other explanations put forth by panicked citizens blamed astrological influences, divine punishment, and the Jewish community. Tens of thousands of Jewish citizens were burned in Spain, Germany, Switzerland, and France despite protests by Pope Clement VI, Emperor Charles IV, and medical experts who said that they were innocent. However, the authorities were powerless to stop the spread of plague, and they were not believed. Quarantines of plague victims were ordered, but they were largely ineffective.

The Black Death was the beginning of a number of plague outbreaks that ravaged Europe and Africa in subsequent centuries. In England alone, there were plague outbreaks in 1361, 1369, 1390, 1413, 1434, 1439, and 1464. Additional outbreaks occurred in Scotland in 1401–1403, 1430–1432, and 1455. The epidemics cut England's population of about seven million in half from 1300 to 1380. The last major outbreaks of the Black Death pandemic occurred in London in 1665–1666 and in Marseilles in 1720–1722. Each of these outbreaks resulted in approximately 100,000 deaths.

In a controversial 2001 book, "Biology of Plagues," authors and epidemiologists Susan Scott and Christopher Duncan write they believe the plague of 1347–1351 was not caused by the bubonic plague, but rather by a still unknown disease. They say the quick spread of the disease and the fact that bubonic plague is not transmitted person to person, as the Black Death was, points to another cause. Another possibility, however, is that the ship trade of that time would have allowed for disease-infested rats to move from location to location rapidly and thus, spread the disease quickly through various populations.

The world's third plague pandemic began in 1894 in China and Hong Kong. Called the Modern Pandemic, it quickly spread throughout the world, carried by rats aboard steamships. From 1894 through 1903, plague-infested ships had brought the disease to 77 ports in Asia, Africa, Europe, North America, Australia , and South America. In India alone, plague killed about 13 million people. In the year the pandemic started, scientists discovered the cause of the disease, and established that rats and their fleas were the carriers.

According to most sources, the Modern Pandemic continues to the present time. Epidemics linked to the Modern pandemic were reported in San Francisco, New Orleans, and other coastal cities throughout the world and millions died. The Modern pandemic also established in areas that previously had been plague free, including North America, South America, and southern Africa. With the advent of antibiotics and the understanding of how plague spreads, the Modern pandemic has been contained and the plague no longer claims millions of victims. However, health authorities remain vigilant because the plague has not been eradicated.

At the turn of the twentieth century, plague outbreaks twice hit San Francisco. The first outbreak was from 1900 to 1904, and the second from 1907 to 1909. Several hundred infections were confirmed but health officials believe hundreds of cases went unreported. More recently, an outbreak of bubonic plague occurred in the African nation of Malawi in early 2002, infecting at least 10 people

The decrease in the incidence of plague today is due primarily to improved living standards and health services in many underdeveloped nations. In India, plague epidemics have stopped altogether. The reasons for this are not clear, according to WHO scientists. The Government of India, however, has taken a number of stringent measures to prevent spread of the disease. These include mandatory screening at airports of every airline passenger intending to travel abroad for signs and symptoms of plague, fumigation of aircraft, including both the passenger cabin and the cargo hold. Additionally, all aircraft are inspected for the presence of rats. At all major sea ports, all out-going vessels are being inspected for the presence of rats and insects. Ships are required to have a certificate, issued by the port health officer, showing that they have been deratted, before they can leave port. All these measures are in accordance with the WHO International Health Regulations.

Plague is often mentioned as a potential biological weapon of terrorists. When released into the air, the bacterium can survive for up to an hour. Of the three types of plague (pneumonic, bubonic, and septicemic), pneumonic is they one most likely to be used by terrorists since large stockpiles were developed by the United States and Soviet Union in the 1950s and 1960s. Much of the Soviet supply is now in the hands of several of its former republics, now independent nations. The U.S. government believes several so-called "rogue" nations, such as Iran, Iraq, and North Korea, have biological weapons programs. While several other nations presumably have biological weapons programs, these nations pose a more significant threat to the United States and its allies.

[Ken R. Wells ]

RESOURCES

BOOKS

Kohn, George C., ed. Encyclopedia of Plague and Pestilence: From Ancient Times to the Present. New York: Facts on File, Inc., 2001.

PERIODICALS

Childress, Diana. "Like Black Smoke, the Black Death's Journey." Calliope (March 2001): 4.

Ligomeka, Brian. "Bubonic Plague Breaks Out in Lilongwe." Africa News Service, May 10, 2002.

Mackenzie, Deborah. "All Fall Down: The Black Death Wasn't Caused by Bubonic Plague, and We Need to Find the Real Culprit Before it Strikes Again." New Scientist (November 24, 2001): 35–38.

McCabe, Suzanne. "Dark Death: In 1347, a Terrible Plague Brought Death and Destruction to Europe." Junior Scholastic (February 11, 2002): 18–22.

Saul, Nigel. "Britain 1400." History Today (July 2000): 38.

"Time Trip. (Black Death)" Current Events, a Weekly Reader Publication, January 11, 2002): 2–3.

Truitt, Elly. "The Medical Response to the Black Death." Calliope (March 2001): 14.

ORGANIZATIONS

World Health Organization Regional Office, 525 23rd Street NW, Washington, DC USA 20037 (202) 974-3000, Fax: (202) 974-3663, Email: [email protected], <http://www.who.int>

Plague

What Is Plague?

How Common Is Plague?

How Is Plague Spread?

What Are the Signs and Symptoms of Plague?

How Do Doctors Diagnose and Treat Plague?

How Can People Prevent Becoming Infected?

Resources

Plague (PLAYG) is a potentially serious bacterial infection that is spread to humans by infected rodents and their fleas.

KEYWORDS

for searching the Internet and other reference sources

Biological weapon

Bioterrorism

Black Death

Buboes

Bubonic plague

Pneumonic plague

Septicemic plague

Yersinia pestis

Zoonoses

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.

*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.

Bioweapons

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.

*biological warfare

is a method of waging war by using harmful microorganisms to purposely spread disease to many people.

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.

*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 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.

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.

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

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.

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*.

*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.

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.

*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.

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.

*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.

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.

*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.

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.

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

*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.

due to lack of blood flow associated with sepsis, brain damage from lack of oxygen, lung damage, and death.

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.

See also

Bioterrorism

Pneumonia

Sepsis

Travel-related Infections

Zoonoses

Resources

Organization

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.

Telephone 800-311-3435 http://www.cdc.gov

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.

Telephone 888-346-3656 http://www.nlm.nih.gov

World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27, Switzerland. WHO provides information about plague at its website.

Telephone 011-41-22-791-2111 http://www.who.int

PLAGUE

Plague is a disease of rodents and their fleas that can be transmitted to humans. Throughout history, plague, often referred to as the "Black Death," has caused catastrophic pandemics resulting in deaths of tens of millions of persons. The disease is caused by a gram-negative bacterium, Yersinia pestis. Humans are usually infected by the bite of infective rodent fleas, but infection also occurs through handling or ingesting infectious animals or by inhaling infective respiratory droplets expelled by humans or animals.

Initial signs and symptoms of plague may be nonspecific, with fever, chills, headache, malaise, musculoskeletal pains, nausea, and weakness leading to prostration. Persons with bubonic plague, the most common form of plague, typically develop painful, swollen lymph nodes near the site of an infective flea bite. Less common forms of plague can infect the bloodstream (septicemic plague), the lungs (pneumonic plague), the throat (pharyngeal plague), or the coverings of the brain (meningeal plague). Pneumonic plague is a severe and rapidly progressive form of the disease that quickly leads to difficulty in breathing, a cough with bloody sputum, and shock.

In any of its clinical forms, plague can be fatal if not diagnosed and treated correctly early in the course of the disease. The diagnosis is made by combining information on possible infective exposures, clinical signs and symptoms, and results from laboratory tests. Treatment, which should begin as soon as the diagnosis is suspected, relies on the aminoglycoside group of antibiotics (streptomycin, gentamicin), tetracyclines (doxycycline, tetracycline, oxytetracycline), chloramphenicol, or trimethoprim-sulfamethoxazole. Laboratory diagnosis is made by direct examination of stained clinical materials, serologies, antigen-detection, isolation of culture media, and molecular-genetic characterizations.

Plague is present in wild rodent populations over large but scattered rural areas of the Americas, Africa, and Asia. Outbreaks sometimes occur among wild rodent populations and occasionally among rat populations in villages and towns, though rarely in cities. When plague involves rats living in or around homes, humans are at their highest risk of exposure. In the United States, plague occurs in the western third of the country, most often in burrowing rodents and their fleas. Plague also occurs in scattered areas of South America, especially the Andean region; in north-central, eastern, and southern Africa; in Madagascar; in several states in the Near East (Saudi Arabia, Yemen, Jordan, and Iranian Kurdistan); central and southern Asia (Georgia, Kazakhstan, Mongolia, China, and India); and Southeast Asia (Myanmar, Vietnam, and Indonesia).

Plague prevention on an individual level involves avoidance of areas of known plague activity, taking personal precautions against flea bites, avoiding sick or dead animals, and seeking medical care at the earliest signs of illness. No vaccine against plague is available in the United States. Pneumonic plague patients should be managed in isolation under respiratory droplet precautions. Postexposure antibiotics may be warranted for persons who, in the previous two days, were likely to have been exposed to infectious fleas or have had close direct exposure to a person or animal with pneumonic plague. Routine community prevention and control of plague is achieved through sanitation and hygiene measures that limit food and harborage for rodents. In the event of a plague outbreak, flea control should be implemented before attempts are made to kill rats.

David T. Dennis

(see also: Black Death; Epidemics; Isolation; Universal Precautions; Vector-Borne Diseases; Zoonoses )

Bibliography

Anonymous (2000). "Plague." In Control of Communicable Diseases Manual, 17th edition, ed. J. Chin. Washington, DC: American Public Health Association.

Dennis, D. T., and Gage, K. G. (1999). "Plague." In Infectious Diseases, Vol. 2, eds. D. Armstrong and J. Cohen. London: Mosby, Armstrong, and Cohen.

Perry, R. D., and Fetherston, J. D. (1997). "Yersinia pestis—Etiologic Agent of Plague." Clinical Microbiological Review 10:35–66.

World Health Organization (1999). Plague Manual: Epidemiology, Distribution, Surveillance and Control. Geneva: Author.