Plague
Classification and external resources
Yersinia pestis seen at 200× magnification with a fluorescent label. This bacterium, carried and spread by fleas, is the cause of the various forms of the disease plague.
ICD-10	A20
ICD-9	020
MedlinePlus	000596
eMedicine	med/3381
MeSH	D010930

Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents (most notably rats) and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death and devastation it brought. Until June 2007, plague was one of the three epidemic diseases specifically reportable to the World Health Organization (the two other ones were cholera and yellow fever).^[1]

Depending on lung infection, or sanitary conditions, plague also can be spread in the air, by direct contact, or by contaminated undercooked food or materials. The symptoms of plague depend on the concentrated areas of infection in each person: such as bubonic plague in lymph nodes, septicemic plague in blood vessels, pneumonic plague in lungs, and so on. It is treatable if detected early. Plague is still endemic in some parts of the world.

Name[link]

The epidemiological use of the term "plague" is currently applied to bacterial infections that cause buboes, although historically the medical use of the term "plague" has been applied to pandemic infections in general. Plague is often synonymous with "bubonic plague" but this describes just one of its manifestations. Other names have been used to describe this disease, such as "The Black Plague" and "The Black Death"; the latter is now used primarily by scholars to describe the second, and most devastating, pandemic of the disease.

The etymology of the word "plague" is believed to come from the Latin word plāga ("blow, wound") and plangere (“to strike, or to strike down”), cf. German Plage (“infestation”).

Epidemiology and distribution[link]

Infection and transmission[link]

The Oriental rat flea (Xenopsylla cheopsis) engorged with blood after a blood meal. This species of flea is the primary vector for the transmission of Yersinia pestis the organism responsible for bubonic plague in most plague epidemics in Asia, Africa, and South America. Both male and female fleas feed on blood and can transmit the infection.

A child bitten by a flea infected with the Yersinia pestis bacteria. Y. pestis-a member of the Enterobacteriaceae family has caused the bite to become ulcerated.

Transmission of Y. pestis to an uninfected individual is possible by any of the following means.^[2]

• droplet contact - coughing or sneezing on another person
• direct physical contact - touching an infected person, including sexual contact
• indirect contact - usually by touching soil contamination or a contaminated surface
• airborne transmission - if the microorganism can remain in the air for long periods
• fecal-oral transmission - usually from contaminated food or water sources
• vector borne transmission - carried by insects or other animals.

Yersinia pestis circulates in animal reservoirs, particularly in rodents, in the natural foci of infection found on all continents except Australia. The natural foci of plague are situated in a broad belt in the tropical and sub–tropical latitudes and the warmer parts of the temperate latitudes around the globe, between the parallels 55 degrees North and 40 degrees South.^[2]

Contrary to popular belief, rats did not directly start the spread of the Bubonic plague. It is mainly a disease in the fleas (Xenopsylla cheopis) that infested the rats, making the rats themselves the first victims of the plague. Infection in a human occurs when a person is bitten by a flea that has been infected by biting a rodent that itself has been infected by the bite of a flea carrying the disease. The bacteria multiply inside the flea, sticking together to form a plug that blocks its stomach and causes it to starve. The flea then bites a host and continues to feed, even though it cannot quell its hunger, and consequently the flea vomits blood tainted with the bacteria back into the bite wound. The bubonic plague bacterium then infects a new victim, and the flea eventually dies from starvation. Serious outbreaks of plague are usually started by other disease outbreaks in rodents, or a rise in the rodent population.

In 1894, two bacteriologists, Alexandre Yersin of France and Kitasato Shibasaburō of Japan, independently isolated the bacterium in Hong Kong responsible for the Third Pandemic. Though both investigators reported their findings, a series of confusing and contradictory statements by Kitasato eventually led to the acceptance of Yersin as the primary discoverer of the organism. Yersin named it Pasteurella pestis in honor of the Pasteur Institute, where he worked, but in 1967 it was moved to a new genus, renamed Yersinia pestis in honor of Yersin. Yersin also noted that rats were affected by plague not only during plague epidemics but also often preceding such epidemics in humans, and that plague was regarded by many locals as a disease of rats: villagers in China and India asserted that, when large numbers of rats were found dead, plague outbreaks soon followed.

In 1898, the French scientist Paul-Louis Simond (who had also come to China to battle the Third Pandemic) established the rat-flea vector that drives the disease. He had noted that persons who became ill did not have to be in close contact with each other to acquire the disease. In Yunnan, China, inhabitants would flee from their homes as soon as they saw dead rats, and on the island of Formosa (Taiwan), residents considered the handling of dead rats heightened the risks of developing plague. These observations led him to suspect that the flea might be an intermediary factor in the transmission of plague, since people acquired plague only if they were in contact with recently dead rats, who had died less than 24 hours before. In a now classic experiment, Simond demonstrated how a healthy rat died of plague, after infected fleas had jumped to it, from a rat which had recently died of the plague.^[3]

Plague immunization[link]

Since human plague is rare in most parts of the world, there is no need to vaccinate people other than those at particularly high risk of exposure. Routine vaccination is not necessary for people living in areas with enzootic plague such as the western United States. It is not indicated for most travellers to countries reporting cases, particularly if their travel is limited to urban areas with modern hotels. The CDC thus only recommends vaccination for: 1) All laboratory and field personnel who are working with Y. pestis organisms resistant to antimicrobials, 2) People engaged in aerosol experiments with Y. pestis and 3) People engaged in field operations in areas with enzootic plague where preventing exposure is not possible (such as some disaster areas).

Pathology[link]

Bubonic plague[link]

Swollen inguinal lymph glands on a person infected with the bubonic plague. The swollen lymph glands are termed buboes from the Greek word for groin, swollen gland: bubo.

When a flea bites a human and contaminates the wound with regurgitated blood, the plague carrying bacteria are passed into the tissue. Y. pestis can reproduce inside cells, so even if phagocytosed, they can still survive. Once in the body, the bacteria can enter the lymphatic system, which drains interstitial fluid. Plague bacteria secrete several toxins, one of which is known to cause dangerous beta-adrenergic blockade.

Y. pestis spreads through the lymphatics of the infected human until it reaches a lymph node, where it stimulates severe haemorrhagic inflammation that causes the lymph nodes to expand. The expansion of lymph nodes is the cause of the characteristic "bubo" associated with the disease.

Septicemic plague[link]

Lymphatics ultimately drain into the bloodstream, so the plague bacteria may enter the blood and travel to almost any part of the body. In septicemic plague, bacterial endotoxins cause disseminated intravascular coagulation (DIC), causing tiny clots throughout the body and possibly ischaemic necrosis (tissue death due to lack of circulation/perfusion to that tissue) from the clots. DIC results in depletion of the body's clotting resources, so that it can no longer control bleeding. Consequently, there is bleeding into the skin and other organs, which can cause red and/or black patchy rash and hemoptysis/hematemesis (coughing up/ vomiting of blood). There are bumps on the skin that look somewhat like insect bites; these are usually red, and sometimes white in the center. Untreated, septicemic plague is usually fatal. Early treatment with antibiotics reduces the mortality rate to between 4 and 15 percent.^[4][5][6] People who die from this form of plague often die on the same day symptoms first appear.

Pneumonic plague[link]

The pneumonic plague infects the lungs, and with that infection comes the possibility of person-to-person transmission through respiratory droplets. The incubation period for pneumonic plague is usually between two and four days, but can be as little as a few hours. The initial symptoms of headache, weakness, and coughing with blood (hemoptysis), or vomiting blood (hematemesis), are indistinguishable from several other respiratory illnesses. Without diagnosis and treatment, the infection can be fatal in one to six days; mortality in untreated cases is approximately 100%.^[7][8]

Pharyngeal plague[link]

This is an uncommon form of plague that resembles tonsillitis found in cases of close contact of patients with other forms of plague.^[9]

Meningeal plague[link]

This form of plague occurs when bacteria cross the blood brain barrier, leading to infectious meningitis.

Other clinical forms[link]

There are a few other rare manifestations of plague, including asymptomatic plague and abortive plague. Cellulocutaneous plague sometimes results in infection of the skin and soft tissue, often around the bite site of a flea.

Treatments[link]

Waldemar Haffkine, a doctor who worked in Mumbai, India, was the first to invent and test a plague vaccine against bubonic plague in 1897.^[10]

If diagnosed in time the various forms of plague are usually highly responsive to antibiotic therapy. The antibiotics often used are Streptomycin, Chloramphenicol and Tetracycline. Amongst the newer generation of antibiotics, Gentamicin and Doxycycline have proven effective in monotherapeutic treatment of plague.^[11]

History[link]

Amulet (800BC-612BC) to ward off plague inscribed with a quotation from the Akkadian Erra Epic.

Nicolas Poussin (1594-1665), French. The Plague of Ashdod, 1630. Oil on canvas, 148 x 198 cm. Musée du Louvre, Paris, France, Giraudon/Bridgeman Art Library.

The earliest account describing a possible plague epidemic is found in I Samuel 5:6 of the Hebrew Bible (Tanakh). In this account, the Philistines of Ashdod were stricken with a plague for the crime of stealing the Ark of the Covenant from the Children of Israel. These events have been dated to approximately the second half of the 11th century BC.^{[citation needed]} The word "tumors" is used in most English translations to describe the sores that came upon the Philistines. The Hebrew, however, can be interpreted as "swelling in the secret parts".^{[citation needed]} The account indicates that the Philistine city and its political territory were stricken with a "ravaging of mice" and a plague, bringing death to a large segment of the population.

In the second year of the Peloponnesian War (430 BC), Thucydides described an epidemic disease which was said to have begun in Ethiopia, passed through Egypt and Libya, then come to the Greek world. In the Plague of Athens, the city lost possibly one third of its population, including Pericles. Modern historians disagree on whether the plague was a critical factor in the loss of the war. Although this epidemic has long been considered an outbreak of plague, many modern scholars believe that typhus,^[12] smallpox, or measles may better fit the surviving descriptions. A recent study of DNA found in the dental pulp of plague victims suggests that typhoid was actually responsible.^[13]

In the first century AD, Rufus of Ephesus, a Greek anatomist, refers to an outbreak of plague in Libya, Egypt, and Syria. He records that Alexandrian doctors named Dioscorides and Posidonius described symptoms including acute fever, pain, agitation, and delirium. Buboes—large, hard, and non-suppurating—developed behind the knees, around the elbows, and "in the usual places." The death toll of those infected was very high. Rufus also wrote that similar buboes were reported by a Dionysius Curtus, who may have practiced medicine in Alexandria in the third century BC. If this is correct, the eastern Mediterranean world may have been familiar with bubonic plague at that early date.^[14][15]

First Pandemic: Plague of Justinian[link]

The Plague of Justinian in AD 541–542 is the first known attack on record, and marks the first firmly recorded pattern of bubonic plague. This disease is thought to have originated in China.^[16] It then spread to Africa from where the huge city of Constantinople imported massive amounts of grain, mostly from Egypt, to feed its citizens. The grain ships were the source of contagion for the city, with massive public granaries nurturing the rat and flea population. At its peak the plague was killing 10,000 people in Constantinople every day and ultimately destroyed perhaps 40% of the city's inhabitants. It went on to destroy up to a quarter of the human population of the eastern Mediterranean.

In AD 588 a second major wave of plague spread through the Mediterranean into what is now France. It is estimated that the Plague of Justinian killed as many as 100 million people across the world.^[17][18] It caused Europe's population to drop by around 50% between 541 and 700.^[19] It also may have contributed to the success of the Arab conquests.^[20][21] An outbreak of it in the AD 560s was described in AD 790 as causing "swellings in the glands...in the manner of a nut or date" in the groin "and in other rather delicate places followed by an unbearable fever". While the swellings in this description have been identified by some as buboes, there is some contention as to whether the pandemic should be attributed to the bubonic plague, Yersinia pestis, known in modern times.^[22]

Second Pandemic: Black Death[link]

"Der Doktor Schnabel von Rom" ("Doctor Beak of Rome"). The beak is a primitive gas mask, stuffed with substances (such as spices and herbs) thought to ward off the plague.

Map showing the spread of the Black Death (bubonic plague) in Europe during the 1347-1351 pandemic which is believed to have started in China and spread west, reaching the Black Sea by 1347.

From 1347 to 1351, the Black Death, a massive and deadly pandemic originating in China, spread along the Silk Road and swept through Asia, Europe and Africa.^[16] It may have reduced the world's population from 450 million to between 350 and 375 million.^[23] China lost around half of its population, from around 123 million to around 65 million; Europe around 1/3 of its population, from about 75 million to about 50 million; and Africa approximately 1/8 of its population, from around 80 million to 70 million (mortality rates tended to be correlated with population density so Africa, being less dense overall, had the lowest death rate). This makes the Black Death the largest death toll from any known non-viral epidemic. Although accurate statistical data does not exist, it is thought that 1.4 million died in England (1/3 of England's 4.2 million people), while an even higher percentage of Italy's population was likely wiped out. On the other hand, Northeastern Germany, Bohemia, Poland and Hungary are believed to have suffered less, and there are no estimates available for Russia or the Balkans. It is conceivable that Russia may not have been as affected due to its very cold climate and large size, hence often less close contact with the contagion.

During the 14th century, it was difficult to pinpoint the exact cause of the Black Death. Many believed it was God punishing the people for their sins. Due to this theory, many began to follow the Flagellants, who inflicted pain upon themselves to absolve their bodies of sin. During the Flagellant's ceremonies, texts were read that were said to be sent by angels to earth. They told of God's and Christ's "anger with rampant impiety" and called for "reform and penance." Through the Flagellant's rituals, it was hoped that people would change their sinful behavior and cause God to call off the Black Death. ^[24]

The Black Death somewhat contributed to the destruction of the feudal system in the Middle Ages, and many of the upper classes were forced to give higher wages and more freedom to their workers willing to work on the nobles' lands because of the high death toll. The Black Death also killed many great kings and nobles, leaving issues with inheritance of land and money left to their families. In its aftermath, the Black Death may also have favoured the use of more advanced farming tools as a smaller workforce was available and plots grew larger as a result of the population loss.

The plague continued to strike parts of Europe sporadically until the 17th century, each time with reduced intensity and fatality, suggesting an increased resistance due to natural selection.^[22] Some have also argued that changes in hygiene habits and efforts to improve public health and sanitation had a significant impact on the falling rates of infection.^[who?] Alternate theories which are just as well grounded in evidence include changes in rat species and rat-human ecology in Europe, to account for the rise and fall of the incidence of plague over the centuries.^[25][26]

Nature of the disease[link]

A hand showing acral gangrene of the digits due to plague, the black appearance of the necrotized tissue which occurs in gangrene, one of the symptoms of plague.

The Roof rat (rattus rattus) is a reservoir host of bubonic plague with the oriental rat fleas that infest them being a prime vector of the disease.

In the early 20th century, following the identification by Yersin and Kitasato of the plague bacterium that caused the late 19th and early 20th century Asian bubonic plague (the Third Pandemic), most scientists and historians came to believe that the Black Death was an incidence of this plague, with a strong presence of the more contagious pneumonic and septicemic varieties increasing the pace of infection, spreading the disease deep into inland areas of the continents. It was claimed that the disease was spread mainly by black rats in Asia and that therefore there must have been black rats in north-west Europe at the time of the Black Death to spread it, although black rats are currently rare except near the Mediterranean. This led to the development of a theory that brown rats had invaded Europe, largely wiping out black rats, bringing the plagues to an end, although there is no evidence for the theory in historical records. Some historians suggest that marmots, rather than rats, were the primary carriers of the disease.^[27]

The view that the Black Death was caused by Yersinia pestis has been incorporated into medical textbooks throughout the 20th century and has become part of popular culture, as illustrated by recent books, such as John Kelly's The Great Mortality. Many modern researchers have argued that the disease was more likely to have been viral (that is, not bubonic plague), pointing to the absence of rats from some parts of Europe that were badly affected and to the conviction of people at the time that the disease was spread by direct human contact. According to the accounts of the time the black death was extremely virulent, unlike the 19th and early 20th century bubonic plague. Samuel K. Cohn has made a comprehensive attempt to rebut the bubonic plague theory.^[28] In the Encyclopedia of Population, he points to five major weaknesses in this theory:

• very different transmission speeds — the Black Death was reported to have spread 385 km in 91 days (4.23 km/day) in 664, compared to 12–15 km a year for the modern Bubonic Plague, with the assistance of trains and cars
• difficulties with the attempt to explain the rapid spread of the Black Death by arguing that it was spread by the rare pneumonic form of the disease — in fact this form killed less than 0.3% of the infected population in its worst outbreak (Manchuria in 1911)
• different seasonality — the modern plague can only be sustained at temperatures between 10 and 26°C and requires high humidity, while the Black Death occurred even in Norway in the middle of the winter and in the Mediterranean in the middle of hot dry summers
• very different death rates — in several places (including Florence in 1348) over 75% of the population appears to have died; in contrast the highest mortality for the modern Bubonic Plague was 3% in Mumbai in 1903
• the cycles and trends of infection were very different between the diseases — humans did not develop resistance to the modern disease, but resistance to the Black Death rose sharply, so that eventually it became mainly a childhood disease

Cohn also points out that while the identification of the disease as having buboes relies on accounts of Boccaccio and others, they described buboes, abscesses, rashes and carbuncles occurring all over the body, the neck or behind the ears. In contrast, the modern disease rarely has more than one bubo, most commonly in the groin, and is not characterised by abscesses, rashes and carbuncles.^[22]

Researchers have offered a mathematical model based on the changing demography of Europe from 1000 to 1800 AD demonstrating how plague epidemics, 1347 to 1670, could have provided the selection pressure that raised the frequency of a mutation to the level seen today that prevent HIV from entering macrophages that carry the mutation (the average frequency of this allele is 10% in European populations).^[29] It is suggested that the original single mutation appeared over 2,500 years ago and that persistent epidemics of a haemorrhagic fever struck at the early classical civilizations.

However recent research published in the open-access scientific journal PloS Pathogens in October 2010 presented conclusive evidence that two previously unknown clades (variant strains) of Y. pestis were responsible for the Black Death.^[30] A multinational team conducted new surveys that used both ancient DNA analyses and protein-specific detection to find DNA and protein signatures specific for Y. pestis in human skeletons from widely distributed mass graves in northern, central and southern Europe that were associated archaeologically with the Black Death and subsequent resurgences. The authors concluded that this research, together with prior analyses from the south of France and Germany,

"...ends the debate about the etiology of the Black Death, and unambiguously demonstrates that Y. pestis was the causative agent of the epidemic plague that devastated Europe during the Middle Ages."

The study also identified two previously unknown but related strains of Y. pestis that were associated with distinct medieval mass graves. These were found to be ancestral to modern isolates of the present-day Y. pestis strains 'Orientalis' and 'Medievalis', suggesting that these variant strains (which are now presumed to be extinct) may have entered Europe in two waves. Surveys of plague pit remains in France and England indicate that the first variant entered Europe through the port of Marseille around November 1347 and spread through France over the next two years, eventually reaching England in the spring of 1349, where it spread through the country in three successive epidemics.

However, surveys of plague pit remains from the Netherlands town of Bergen op Zoom showed evidence of a second Y. pestis genotype which differed from that found in Britain and France and this second strain is now thought to have been responsible for the pandemic that spread through the Low Countries from 1350. This discovery implies that Bergen op Zoom (and possibly other parts of the southern Netherlands) was not directly infected from England or France c. AD 1349, and the researchers have suggested that a second wave of plague infection, distinct from that which occurred in Britain and France, may have been carried to the Low Countries from Norway, the Hanseatic cities, or another site.^[30]

Third Pandemic[link]

Houses being burned in China in the 1890's during the bubonic plague pandemic

The Third Pandemic began in China's Yunnan province in 1855, spreading plague to all inhabited continents and ultimately killing more than 12 million people in India and China alone. Casualty patterns indicate that waves of this pandemic may have come from two different sources. The first was primarily bubonic and was carried around the world through ocean-going trade, transporting infected persons, rats, and cargoes harboring fleas. The second, more virulent strain was primarily pneumonic in character, with a strong person-to-person contagion. This strain was largely confined to Manchuria and Mongolia. Researchers during the "Third Pandemic" identified plague vectors and the plague bacterium (see above), leading in time to modern treatment methods.

Plague occurred in Russia in 1877–1889 in rural areas near the Ural Mountains and the Caspian Sea. Efforts in hygiene and patient isolation reduced the spread of the disease, with approximately 420 deaths in the region. Significantly, the region of Vetlianka in this area is near a population of the bobak marmot, a small rodent considered a very dangerous plague reservoir. The last significant Russian outbreak of Plague was in Siberia in 1910 after sudden demand for Marmot skins (a substitute for Sable) increased the price by 400 percent. The traditional hunters would not hunt a sick Marmot and it was taboo to eat the fat from under the arm (the axillary lymphatic gland that often harboured the plague) so outbreaks tended to be confined to single individuals. The price increase, however, attracted thousands of Chinese hunters from Manchuria who not only caught the sick animals but also ate the fat, which was considered a delicacy. The plague spread from the hunting grounds to the terminus of the Chinese Eastern Railway and then followed the track for 2,700 km. The plague lasted 7 months and killed 60,000 people.

The bubonic plague continued to circulate through different ports globally for the next fifty years; however, it was primarily found in Southeast Asia. An epidemic in Hong Kong in 1894 had particularly high death rates, 90%.^[31] As late as 1897, medical authorities in the European powers organized a conference in Venice, seeking ways to keep the plague out of Europe. Mumbai plague epidemic struck the city of Mumbai (Bombay) in 1896. The disease reached the Territory of Hawaii in December 1899, and the Board of Health's decision to initiate controlled burns of select buildings in Honolulu's Chinatown turned into an uncontrolled fire which led to the inadvertent burning of most of Chinatown on January 20, 1900.^[32] Shortly thereafter, plague reached the continental US, initiating the San Francisco plague of 1900–1904. Plague persisted in Hawaii on the outer islands of Maui and Hawaii (The Big Island) until it was finally eradicated in 1959.^[33]

Although the outbreak that began in China in 1855 is conventionally known as the Third Pandemic, (see above), it is unclear whether there have been fewer, or more, than three major outbreaks of bubonic plague. Most modern outbreaks of bubonic plague amongst humans have been preceded by a striking, high mortality amongst rats, yet this phenomenon is absent from descriptions of some earlier plagues, especially the Black Death. The buboes, or swellings in the groin, that are especially characteristic of bubonic plague, are a feature of other diseases as well.

Research done by a team of biologists from the Institute of Pasteur in Paris and Johannes Gutenberg University Mainz in Germany by analyzing the DNA and proteins from plague pits was published in Oct., 2010, reported beyond doubt that all 'the three major plagues' were due to at least two previously unknown strains of Yersinia pestis and originated from China. A team of medical geneticists led by Mark Achtman of University College Cork in Ireland reconstructed a family tree of the bacterium and concluded in an online issue of Nature Genetics published on 31 Oct., 2010 that all three of the great waves of plague originated from China. Europe’s Plagues Came From China, Study Finds.

Plague as a biological weapon[link]

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Worldwide distribution of plague infected animals 1998

Plague has a long history as a biological weapon. Historical accounts from ancient China and medieval Europe detail the use of infected animal carcasses, such as cows or horses, and human carcasses, by the Xiongnu/Huns, Mongols, Turks, and other groups, to contaminate enemy water supplies. Han Dynasty General Huo Qubing is recorded to have died of such a contamination while engaging in warfare against the Xiongnu. Plague victims were also reported to have been tossed by catapult into cities under siege.

In 1347, the Genoese possession of Caffa, a great trade emporium on the Crimean peninsula, came under siege by an army of Mongol warriors of the Golden Horde under the command of Janibeg. After a protracted siege during which the Mongol army was reportedly withering from the disease, they decided to use the infected corpses as a biological weapon. The corpses were catapulted over the city walls, infecting the inhabitants. The Genoese traders fled, transferring the plague (Black Death) via their ships into the south of Europe, whence it rapidly spread.^[34]

During World War II, the Japanese Army developed weaponised plague, based on the breeding and release of large numbers of fleas. During the Japanese occupation of Manchuria, Unit 731 deliberately infected Chinese, Korean, and Manchurian civilians and prisoners of war with the plague bacterium. These subjects, termed "maruta", or "logs", were then studied by dissection, others by vivisection while still conscious. Members of the unit such as Shiro Ishii were exonerated from the Tokyo tribunal by Douglas MacArthur but 12 of them were prosecuted in the Khabarovsk War Crime Trials in 1949 during which some admitted having spread Bubonic plague within a 36-km radius around the city of Changde.^[35]

Ishii innovated bombs containing live mice and fleas, with very small explosive loads, to deliver the weaponized microbes, overcoming the problem of the explosive killing the infected animal and insect by the use of a ceramic, rather than metal, casing for the warhead. While no records survive of the actual usage of the ceramic shells, prototypes exist and are believed to have been used in experiments during WWII.

After World War II, both the United States and the Soviet Union developed means of weaponising pneumonic plague. Experiments included various delivery methods, vacuum drying, sizing the bacterium, developing strains resistant to antibiotics, combining the bacterium with other diseases (such as diphtheria), and genetic engineering. Scientists who worked in USSR bio-weapons programs have stated that the Soviet effort was formidable and that large stocks of weaponised plague bacteria were produced. Information on many of the Soviet projects is largely unavailable. Aerosolized pneumonic plague remains the most significant threat. The plague can be easily treated with antibiotics, thus a widespread epidemic is highly unlikely in developed countries.

1994 epidemic in Surat, India[link]

In 1994, there was a pneumonic plague epidemic in Surat, India that resulted in 52 deaths and in a large internal migration of about 300,000 residents, who fled fearing quarantine.^[36]

A combination of heavy monsoon rain and clogged sewers led to massive flooding which resulted in unhygienic conditions and a number of uncleared animal carcasses. It is believed that this situation precipitated the epidemic.^[37] There was widespread fear that the flood of refugees might spread the epidemic to other parts of India and the world, but that scenario was averted, probably as a result of effective public health response mounted by the Indian health authorities.^[38]

Much like the Black Death that spread through medieval Europe, some questions still remain unanswered about the 1994 epidemic in Surat.^[39]

Initial questions about whether it was an epidemic of plague arose because the Indian health authorities were unable to culture Yersinia pestis, but this could have been due to poor laboratory procedures.^[39] Yet, there are several lines of evidence strongly suggesting that it was a plague epidemic: blood tests for Yersinia were positive, a number of individuals showed antibodies against Yersinia and the clinical symptoms displayed by the affected were all consistent with the disease being plague.^[40]

Other contemporary cases[link]

• On August 31, 1984, the Centers for Disease Control and Prevention reported a case of pneumonic plague in Claremont, California. The CDC believes that the patient, a veterinarian, contracted plague from a stray cat. As the cat wasn't available for necropsy, this could not be ultimately confirmed.^[41]
• From 1995 to 1998, annual outbreaks of plague were witnessed in Mahajanga, Madagascar.^[42]
• In the U.S., about half of all fatal cases of plague since 1970 have occurred in New Mexico. There were 2 plague deaths in the state in 2006, the first fatalities in 12 years.^[43]
• In February 2002, a small outbreak of pneumonic plague took place in the Shimla District of Himachal Pradesh state in northern India.^[44]
• In Fall of 2002, a New Mexico couple contracted the disease, just prior to a visit to New York City. They both were treated by antibiotics, but the male required amputation of both feet to fully recover, due to the lack of blood flow to his feet, cut off by the bacteria.
• On April 19, 2006, CNN News and others reported a case of plague in Los Angeles, California, lab technician Nirvana Kowlessar, the first reported case in that city since 1984.^[45]
• In May 2006, KSL Newsradio reported a case of plague found in dead field mice and chipmunks at Natural Bridges National Monument about 40 miles (64 km) west of Blanding in San Juan County, Utah.^[46]
• In May 2006, Arizona media reported a case of plague found in a cat.^[47]
• One hundred deaths resulting from pneumonic plague were reported in Ituri district of the eastern Democratic Republic of the Congo in June 2006. Control of the plague was proving difficult due to the ongoing conflict.^[48]
• It was reported in September 2006 that three mice infected with Yersinia pestis apparently disappeared from a laboratory belonging to the Public Health Research Institute, located on the campus of the University of Medicine and Dentistry of New Jersey, which conducts anti-bioterrorism research for the United States government.^[49]
• On May 16, 2007, an 8-year-old hooded capuchin monkey in the Denver Zoo died of the bubonic plague. Five squirrels and a rabbit were also found dead on zoo grounds and tested positive for the disease.^[50]
• On June 5, 2007 in Torrance County, New Mexico a 58 year old woman developed bubonic plague, which progressed to pneumonic plague.^[51]
• On November 2, 2007, Eric York, a 37 year old wildlife biologist for the National Park Service's Mountain Lion Conservation programPDF (144 KB) and The Felidae Conservation Fund, was found dead in his home at Grand Canyon National Park. On October 27, York performed a necropsy on a mountain lion that had likely perished from the disease and three days afterward York complained of flu-like symptoms and called in sick from work. He was treated at a local clinic but was not diagnosed with any serious ailment. The discovery of his death sparked a minor health scare, with officials stating he likely died of either plague or hantavirus, and 49 people who had come in to contact with York were given aggressive antibiotic treatments. None of them fell ill. Autopsy results released on November 9, confirmed the presence of Y. pestis in his body, confirming plague as a likely cause of death.^[52][53]
• In January 2008, at least 18 people died of bubonic plague in Madagascar.^[54]
• On June 16, 2009, Libyan authorities reported an outbreak of bubonic plague in Tobruk, Libya. 16-18 cases were reported, including one death.^[55]
• On August 2, 2009, Chinese authorities quarantined the town of Ziketan, Xinghai County in Hainan Tibetan Autonomous Prefecture, Qinghai Province (Northwestern China) after an outbreak of pneumonic plague. As of this writing, three have died and ten more are ill, being treated in hospital.^[56]
• On September 13, 2009, Dr. Malcolm Casadaban died following an accidental laboratory exposure to an attenuated strain of the plague bacterium. This has happened due to his undiagnosed hereditary hemochromatosis (iron overload). He was an Associate Professor of Molecular Genetics and Cell Biology and of Microbiology at the University of Chicago.^[57]
• On 1 July 2010, 8 cases of Bubonic plague were reported in humans in the District of Chicama, Peru. One 32 year old man was affected, as well as 3 boys and 4 girls ranging in age from 8 to 14 years old. 425 houses were fumigated and 1210 guinea pigs, 232 dogs, 128 cats and 73 rabbits were given anti flea treatment in an effort to stop the epidemic.^[58]
• On May 3, 2012, a ground squirrel trapped during routine testing at a popular campground on Palomar Mountain in San Diego County, California, tested positive for the plague bacteria.^[59]

References[link]

Notes[link]

Bibliography[link]

• Weatherford 2004: 242-250
• Benedictow, Ole J. The Black Death 1346-1353: The Complete History. DS Brewer, 2006. ISBN 978-1-84383-214-0.
• Biraben, Jean-Noel. Les Hommes et la Peste The Hague 1975.
• Buckler, John and Bennet D. Hill and John P. McKay. "A History of Western Society, 5th Edition." New York: Houghton Mifflin Co., 1995.
• Cantor, Norman F., In the Wake of the Plague: the Black Death and the World It Made New York: Harper Perennial, 2002. ISBN 978-0-06-001434-6.
• de Carvalho RW, Serra-Freire NM, Linardi PM, de Almeida AB, da Costa JN (July 2001). "Small rodents fleas from the bubonic plague focus located in the Serra dos Orgãos Mountain Range, State of Rio de Janeiro, Brazil". Mem. Inst. Oswaldo Cruz 96 (5): 603–9. DOI:10.1590/S0074-02762001000500003. PMID 11500756. . this manuscript reports a census of potential plague vectors (rodents and fleas) in a Brazilian focus region (i.e. region associated with cases of disease); free PDF download Retrieved 2005-03-02
• Chase, Marilyn. The Barbary Plague: The Black Death in Victorian San Francisco. New York: Random House Trade Paperbacks, 2004. ISBN 978-0-375-75708-2.
• Cohn, Samuel K. (2003). The Black Death Transformed: Disease and Culture in Early Renaissance Europe. A Hodder Arnold. pp. 336. ISBN 0-340-70646-5. 
• Gregg, Charles T. Plague!: The shocking story of a dread disease in America today. New York, NY: Scribner, 1978, ISBN 0-684-15372-6.
• Ernest Jawetz, and others. Medical Microbiology. 18th ed. United States: Prentice-Hall International Inc., 1989. ISBN 0-8385-6238-8
• Kelly, John. The Great Mortality: An Intimate History of the Black Death, the Most Devastating Plague of All Time. New York: HarperCollins Publishers Inc., 2005. ISBN 0-06-000692-7.
• McNeill, William H. Plagues and People. New York: Anchor Books, 1976. ISBN 0-385-12122-9. Reprinted with new preface 1998.
• Mohr, James C. Plague and Fire: Battling Black Death and the 1900 Burning of Honolulu's Chinatown. New York, NY: Oxford University Press, 2005, ISBN 0-19-516231-5.
• Moote, A. Lloyd, and Dorothy C. Moote. The Great Plague: The Story of London's Most Deadly Year. Baltimore, MD: Johns Hopkins University Press, 2004. ISBN 978-0-8018-7783-4.
• Orent, Wendy. Plague: The Mysterious Past and Terrifying Future of the World's Most Dangerous Disease. New York: Free Press, 2004. ISBN 0-7432-3685-8.
• Patrick, Adam. "Disease in Antiquity: Ancient Greece and Rome," in Diseases in Antiquity, editors: Don Brothwell and A. T. Sandison. Springfield, Illinois; Charles C. Thomas, 1967.
• Platt, Colin. King Death: The Black Death and its Aftermath in Late-Medieval England Toronto University Press, 1997.
• Rosen, William (2007). Justinian's Flea: Plague, Empire, and the Birth of Europe. Viking Penguin. pp. 367. ISBN 978-0-670-03855-8. 
• Simpson, W. J. A Treatise on Plague. Cambridge, England: Cambridge University Press, 1905.
• Spielvogel, Jackson J. Western Civilization: A Brief History Vol. 1: to 1715. Belmont, Calif.: West/Wadsworth, 1999, Ch. 3, p. 56, paragraph 2. ISBN 0-534-56062-8.

External links[link]

• World Health Organization
  • Health topic
  • Communicable Disease Surveillance & Response - Impact of plague & Information resources
• Centers for Disease Control and Prevention
  • CDC Plague map world distribution, publications, information on bioterrorism preparedness and response regarding plague
  • Infectious Disease Information more links including travelers' health
• Agent Fact Sheet: Plague, Center for Biosecurity
• Symptoms, causes, pictures of bubonic plague
• Secrets of the Dead. Mystery of the Black Death PBS
• Flea As WeaponPDF (281 KB)
• Researchers sound the alarm: the multidrug resistance of the plague bacillus could spread
• Plague - LoveToKnow 1911
• Genome information is available from the NIAID PathoSystems Resource Integration Center (PATRIC)
• The photos & video of the Plague (on the skin of the legs)

Look up plague or plagues in Wiktionary, the free dictionary.

Plague or The Plague may refer to:

Medicine[link]

• Plague (disease), a specific disease caused by Yersinia pestis. There are three major manifestations:
  • Bubonic plague
  • Septicemic plague
  • Pneumonic plague
• An epidemic of infectious disease
• A pandemic caused by such a disease

Art and literature[link]

• Plague (Böcklin), a painting by Arnold Böcklin
• Plague, a 2000 novel by Malcolm Rose
• Plague 99, a 1989 novel by Jean Ure
• The Plague, a 1947 novel by Albert Camus
• The Plague (Dragon Prince), an epidemic in Melanie Rawn's fantasy novel Dragon Prince
• The Plague (magazine), New York University's comedy magazine

Film and television[link]

• Plague (1978 film), a science-fiction genre film depicting a genetic engineering accident
• The Plague (film), a 2006 horror film
• "The Plague" (Diagnosis Murder Episode), a 1994 episode of Diagnosis Murder
• "The Plague", second episode of the 1966 Doctor Who serial The Ark
• "The Plague" (Father Ted), a 1996 episode of Father Ted
• "Plague" (Dead Zone), a 2003 episode of Dead Zone
• "Plague" (Deadwood episode), a 2004 episode of Deadwood

Music[link]

• The Plague (American band), a hardcore punk band from Cleveland
• The Plague (English band), an English punk rock band
• The Plague (New Zealand band)
• Plague! The Musical, a 2008 musical by David Massingham and Matthew Townend
• Plagues (album), a 2007 album by The Devil Wears Prada
• The Plague, a 1983 album by Demon
• The Plague (Brotha Lynch Hung album), 2002
• The Plague (EP), a 1987 EP by Nuclear Assault
• The Plague EP, a 2005 EP by I Hate Sally
• Plague (Klinik album), a 1987 album by Klinik

Other[link]

• Plague (comics), a Marvel Comics character
• The Plague, a Cobra special forces team in the comic G.I. Joe: America's Elite
• The Plague, a duo of demonic assassins in the movie Hobo with a Shotgun

See also[link]

• List of epidemics
• Antonine Plague, an ancient pandemic in 165–189 AD brought to the Roman Empire by troops returning from campaigns in the Near East
• Black Death, also known as The Black Plague: the Eurasian pandemic beginning in the 14th century
• Capacitor plague, a condition afflicting computer motherboards in which capacitors fail
• Corrupted Blood incident, a virtual plague that occurred in the video game World of Warcraft
• Great Plague of London, a massive outbreak in England that killed an estimated 20% of London's population in 1665–1666
• Plague of Athens, a devastating epidemic which hit Athens in ancient Greece in 430 BC
• Plague of Justinian, a pandemic in 541–542 AD in the Byzantine Empire
• Plague Riot, a riot in Moscow in 1771 caused by an outbreak of bubonic plague
• Plagues of Egypt, the 10 calamities that God inflicted on Egypt in the book of Exodus
• Third Pandemic, a major plague pandemic that began in China in 1855
• Overpopulation (animals)#Wild animal overpopulation afflicting the environment and/or agriculture
• A massive attack of Pest over agriculture
• Plague is a term for a large group of common Grackles
• Plaque (disambiguation)

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs.^[1] It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune diseases. In humans, "disease" is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the person afflicted, or similar problems for those in contact with the person. In this broader sense, it sometimes includes injuries, disabilities, disorders, syndromes, infections, isolated symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories. Diseases usually affect people not only physically, but also emotionally, as contracting and living with many diseases can alter one's perspective on life, and their personality.

Death due to disease is called death by natural causes. There are four main types of disease: pathogenic disease, deficiency disease, hereditary disease, and physiological disease.

Diseases can also be classified as communicable and non-communicable disease.

Terminology[link]

In many cases, the terms disease, disorder, morbidity and illness are used interchangeably.^[2] In some situations, specific terms are considered preferable.

Disease[link]

The term disease broadly refers to any condition that impairs normal function. Commonly, this term is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions. An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, is not considered a disease; by contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, and genetic disease.

Illness[link]

Illness and sickness are generally used as synonyms for disease.^[3] However, this term is occasionally used to refer specifically to the patient's personal experience of their disease.^[4][5] In this model, it is possible for a person to be diseased without being ill (to have an objectively definable, but asymptomatic, medical condition), and to be ill without being diseased (such as when a person perceives a normal experience as a medical condition, or medicalizes a non-disease situation in his or her life). Illness is often not due to infection but a collection of evolved responses, sickness behavior, by the body which aids the clearing of infection. Such aspects of illness can include lethargy, depression, anorexia, sleepiness, hyperalgesia, and inability to concentrate.^[6][7][8]

Disorder[link]

In medicine, a disorder is a functional abnormality or disturbance. Medical disorders can be categorized into mental disorders, physical disorders, genetic disorders, emotional and behavioral disorders, and functional disorders.

The term disorder is often considered more value-neutral and less stigmatizing than the terms disease or illness, and therefore is preferred terminology in some circumstances. In mental health, the term mental disorder is used as a way of acknowledging the complex interaction of biological, social, and psychological factors in psychiatric conditions. However, the term disorder is also used in many other areas of medicine, primarily to identify physical disorders that are not caused by infectious organisms, such as metabolic disorders.

Medical condition[link]

A medical condition is a broad term that includes all diseases and disorders. While the term medical condition generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses. The Diagnostic and Statistical Manual of Mental Disorders (DSM), the widely used psychiatric manual that defines all mental disorders, uses the term general medical condition to refer to all diseases, illnesses, and injuries except for mental disorders.^[9] This usage is also commonly seen in the psychiatric literature. Some health insurance policies also define a medical condition as any illness, injury, or disease except for psychiatric illnesses.^[10]

As it is more value-neutral than terms like disease, the term medical condition is sometimes preferred by people with health issues that they do not consider to be deleterious. On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.

The term medical condition is used as a synonym for medical state, where it describes a patient's current state, as seen from a medical standpoint. This usage is seen in statements that describe a patient as being "in critical condition", for example.

[edit] Morbidity

Morbidity (from Latin morbidus, meaning "sick, unhealthy") is a diseased state, disability, or poor health due to any cause.^[11] The term may be used to refer to the existence of any form of disease, or to the degree that the health condition affects the patient. Among severely ill patients, the level of morbidity is often measured by ICU scoring systems.

Comorbidity is the simultaneous presence of two medical conditions, such as a person with schizophrenia and substance abuse.

In epidemiology and actuarial science, the term morbidity rate can refer to either the incidence rate, or the prevalence of a disease or medical condition. This measure of sickness is contrasted with the mortality rate of a condition, which is the proportion of people dying during a given time interval.

Stages[link]

In an infectious disease, the incubation period is the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state. For example, varicella zoster virus causes chickenpox in the acute phase; after recovery from chickenpox, the virus may remain dormant in nerve cells for many years, and later cause herpes zoster (shingles).

A cure is the end of a medical condition or a treatment that is very likely to end it, while remission refers to the disappearance, possibly temporarily, of symptoms. Complete remission is the best possible outcome for incurable diseases.

A flare-up can refer to either the recurrence of symptoms or an onset of more severe symptoms.

A refractory disease is a disease that resists treatment, especially an individual case that resists treatment more than is normal for the specific disease in question.

Progressive disease is a disease whose typical natural course is the worsening of the disease until death, serious debility, or organ failure occurs. Slowly progressive diseases are also chronic diseases; many are also degenerative diseases. The opposite of progressive disease is stable disease or static disease: a medical condition that exists, but does not get better or worse.

Scope[link]

A localized disease is one that affects only one part of the body, such as athlete's foot or an eye infection.

A disseminated disease has spread to other parts; with cancer, this is usually called metastatic disease.

A systemic disease is a disease that affects the entire body, such as influenza or high blood pressure.

Causes and transmissibility[link]

Only some diseases such as influenza are contagious and commonly believed to be infectious. The micro-organisms that cause these diseases are known as pathogens and include varieties of bacteria, viruses, protozoa and fungi. Infectious diseases can be transmitted, e.g. by hand-to-mouth contact with infectious material on surfaces, by bites of insects or other carriers of the disease, and from contaminated water or food (often via faecal contamination), etc. In addition, there are sexually transmitted diseases. In some cases, micro-organisms that are not readily spread from person to person play a role, while other diseases can be prevented or ameliorated with appropriate nutrition or other lifestyle changes.

Some diseases, such as most (but not all) forms of cancer, heart disease and mental disorders, are non-infectious diseases. Many non-infectious diseases have a partly or completely genetic basis (see genetic disorder) and may thus be transmitted from one generation to another.

Social determinants of health are the social conditions in which people live which determine their health. Illnesses are generally related to social, economic, political, and environmental circumstances. Social determinants of health have been recognized by several health organizations such as the Public Health Agency of Canada and the World Health Organization to greatly influence collective and personal well-being. The World Health Organization's Social Determinants Council also recognizes Social determinants of health in poverty.

When the cause of a disease is poorly understood, societies tend to mythologize the disease or use it as a metaphor or symbol of whatever that culture considers to be evil. For example, until the bacterial cause of tuberculosis was discovered in 1882, experts variously ascribed the disease to heredity, a sedentary lifestyle, depressed mood, and overindulgence in sex, rich food, or alcohol—all the social ills of the time.^[12]

Burdens of disease[link]

Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators.

There are several measures used to quantify the burden imposed by diseases on people. The years of potential life lost (YPLL) is a simple estimate of the number of years that a person's life was shortened due to a disease. For example, if a person dies at the age of 65 from a disease, and would probably have lived until age 80 without that disease, then that disease has caused a loss of 15 years of potential life. YPLL measurements do not account for how disabled a person is before dying, so the measurement treats a person who dies suddenly and a person who died at the same age after decades of illness as equivalent. In 2004, the World Health Organization calculated that 932 million years of potential life were lost to premature death.^[13]

The quality-adjusted life year (QALY) and disability-adjusted life year (DALY) metrics are similar, but take into account whether the person was healthy after diagnosis. In addition to the number of years lost due to premature death, these measurements add part of the years lost to being sick. Unlike YPLL, these measurements show the burden imposed on people who are very sick, but who live a normal lifespan. A disease that has high morbidity, but low mortality, will have a high DALY and a low YPLL. In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury.^[13]

Prevention[link]

Many diseases and disorders can be prevented through a variety of means. These include sanitation, proper nutrition, adequate exercise, vaccinations, and other self-care and public health measures.

Treatments[link]

Medical therapies or treatments are efforts to cure or improve a disease or other health problem. In the medical field, therapy is synonymous with the word "treatment". Among psychologists, the term may refer specifically to psychotherapy or "talk therapy". Common treatments include medications, surgery, medical devices, and self-care. Treatments may be provided by an organized health care system, or informally, by the patient or family members.

A prevention or preventive therapy is a way to avoid an injury, sickness, or disease in the first place. A treatment or cure is applied after a medical problem has already started. A treatment attempts to improve or remove a problem, but treatments may not produce permanent cures, especially in chronic diseases. Cures are a subset of treatments that reverse diseases completely or end medical problems permanently. Many diseases that cannot be completely cured are still treatable.Pain management (also called pain medicine) is that branch of medicine employing an interdisciplinary approach to the relief of pain and improvement in the quality of life of those living with pain^[14]

Treatment for medical emergencies must be provided promptly, often through an emergency department or, in less critical situations, through an urgent care facility.

Epidemiology[link]

Epidemiology is the study of the factors that cause or encourage diseases. Some diseases are more common in certain geographic areas, among people with certain genetic or socioeconomic characteristics, or at different times of the year.

Epidemiology is considered a cornerstone methodology of public health research, and is highly regarded in evidence-based medicine for identifying risk factors for disease. In the study of communicable and non-communicable diseases, the work of epidemiologists ranges from outbreak investigation to study design, data collection and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. Epidemiologists rely on a number of other scientific disciplines such as biology (to better understand disease processes), biostatistics (the current raw information available), Geographic Information Science (to store data and map disease patterns) and social sciencedisciplines (to better understand proximate and distal risk factors).

In studying diseases, epidemiology faces the challenge of defining them. Especially for poorly understood diseases, different groups might use significantly different definitions. Without an agreed-upon definition, different researchers will find very different numbers of cases and characteristics of the disease.^[15]

Social and culture[link]

Obesity was a status symbol in Renaissance culture: "The Tuscan General Alessandro del Borro", attributed to Andrea Sacchi, 1645.^[16] It is now generally regarded as a disease.

How society responds to disease is the subject of medical sociology.

A condition may be considered to be a disease in some cultures or eras but not in others. For example, obesity can represent wealth and abundance, and is a status symbol in famine-prone areas and some places hard-hit by HIV/AIDS.^[17] Epilepsy is considered a sign of spiritual gifts among the Hmong people.^[18]

Sickness confers the social legitimization of certain benefits, such as illness benefits, work avoidance, and being looked after by others. The person who is sick takes on a social role called the sick role. A person who responds to a dreaded disease, such as cancer, in a culturally acceptable fashion may be publicly and privately honored with higher social status.^[19] In return for these benefits, the sick person is obligated to seek treatment and work to become well once more. As a comparison, consider pregnancy, which is not usually interpreted as a disease or sickness, even if the mother and baby may both benefit from medical care.

Most religions grant exceptions from religious duties to people who are sick. For example, one whose life would be endangered by fasting on Yom Kippur or during Ramadan is exempted from the requirement, or even forbidden from participating. People who are sick are also exempted from social duties. For example, ill health is the only socially acceptable reason for an American to refuse an invitation to the White House.^[20]

The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognitions as diseases of post-traumatic stress disorder, also known as "Soldier's heart", "shell shock", and "combat fatigue;" repetitive motion injury or repetitive stress injury (RSI); and Gulf War syndrome has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing aging as a disease could be profound, though this classification is not yet widespread. Lepers were a group of afflicted individuals who were historically shunned and the term "leper" still evokes social stigma. Fear of disease can still be a widespread social phenomenon, though not all diseases evoke extreme social stigma.

Social standing and economic status affect health. Diseases of poverty are diseases that are associated with poverty and low social status; diseases of affluence are diseases that are associated with high social and economic status. Which diseases are associated with which states varies according to time, place, and technology. Some diseases, such as diabetes mellitus, may be associated with both poverty (poor food choices) and affluence (long lifespans and sedentary lifestyles), through different mechanisms. The term diseases of civilization describes diseases that are more common among older people. For example, cancer is far more common in societies in which most members live until they reach the age of 80 than in societies in which most members die before they reach the age of 50.

Language of disease[link]

An illness narrative is a way of organizing a medical experience into a coherent story that illustrates the experience.

People use metaphors to make sense of their experiences with disease. The metaphors move disease from an objective thing that exists to an affective experience. The most popular metaphors draw on military concepts: Disease is an enemy that must be feared, fought, battled, and routed. The patient or the physician is a warrior, rather than a passive victim or bystander. The agents of communicable diseases are invaders; non-communicable diseases constitute internal insurrection. Because the threat is urgent, perhaps a matter of life and death, unthinkably radical, even oppressive, measures are society's and the patient's moral duty as they courageously mobilize to struggle against destruction. The War on Cancer is an example.^[21]

Another class of metaphors describes the experience of illness as a journey: The person travels to or from a place of disease, and changes himself, discovers new information, or increases his experience along the way. He may travel "on the road to recovery" or make changes to "get on the right track".^[21] Some are explicitly immigration-themed: the patient has been exiled from the home territory of health to the land of the ill, changing identity and relationships in the process.^[22]

Some metaphors are disease-specific. Slavery is a common metaphor for addictions: The alcoholic is enslaved by drink, and the smoker is captive to nicotine. Some cancer patients treat the loss of their hair from chemotherapy as a metonymy or metaphor for all the losses caused by the disease.^[21]

Some diseases are used as metaphors for social ills: "Cancer" is a common description for anything that is endemic and destructive in society, such as poverty, injustice, or racism. AIDS was seen as a divine judgment for moral decadence, and only by purging itself from the "pollution" of the "invader" could society become healthy again.^[21] Authors in the 19th century commonly used tuberculosis as a symbol and a metaphor for transcendence. Victims of the disease were portrayed in literature as having risen above daily life to become ephemeral objects of spiritual or artistic achievement. In the 20th century, the same disease became the emblem of poverty, squalor, and other social problems.^[22]

See also[link]

• List of acronyms on diseases and disorders
• List of cutaneous conditions
• Lists of diseases
• Airborne disease, a disease that spreads through the air
• Contagious disease, a subset of infectious diseases
• Cryptogenic disease, a disease whose cause is currently unknown
• Disseminated disease, a disease that is spread throughout the body
• Environmental disease
• Lifestyle disease, a disease caused largely by lifestyle choices
• Localized disease, a disease affecting one body part or area
• Non-communicable disease, a disease that can't be spread between people
• Organic disease
• Progressive disease, a disease that gets worse over time
• Rare disease, a disease that affects very few people
• Systemic disease, a disease affecting the whole body
• Plant pathology
• Sociology of health and illness
• List of mystery diseases

References[link]