The three types of plague are the result of the route of infection: bubonic plague,septicemic plague, andpneumonic plague.[1] Bubonic plague is mainly spread by infectedfleas from smallanimals.[1] It may also result from exposure to the body fluids from a dead plague-infected animal.[6] Mammals such asrabbits,hares, and somecat species are susceptible to bubonic plague, and typically die upon contraction.[7] In the bubonic form of plague, the bacteria enter through the skin through a flea bite and travel via thelymphatic vessels to alymph node, causing it to swell.[1] Diagnosis is made by finding the bacteria in the blood,sputum, or fluid from lymph nodes.[1]
Without treatment, plague results in the death of 30% to 90% of those infected.[1][4] Death, if it occurs, is typically within 10 days.[9] With treatment, the risk of death is around 10%.[4] Globally between 2010 and 2015 there were 3,248 documented cases, which resulted in 584 deaths.[1] The countries with the greatest number of cases are theDemocratic Republic of the Congo,Madagascar, andPeru.[1]
The bubonic plague is an infection of thelymphatic system, usually resulting from the bite of an infected flea,Xenopsylla cheopis (the Oriental rat flea),[14] though other flea species are able to carry the bubonic plague, such asPulex irritans (the human flea) andCeratophyllus fasciatus.[14]Xenopsylla cheopis was the most effective flea species for transmission.[14]
The flea isparasitic onhouse andfield rats and seeks out other hosts when its rodent host dies. Rats were an amplifying factor to bubonic plague due to their common association with humans (living around and withindwellings) as well as the nature of their blood, which allows the rat to withstand a majorconcentration of the plague.[15][clarification needed] The bacteria form aggregates in the gut of infected fleas, and this results in the flea regurgitating ingested blood, which is now infected, into the bite site of a rodent or human host. Once established, the bacteria rapidly spread to thelymph nodes of the host and multiply. The fleas that transmit the disease only directly infect humans when the ratpopulation in thearea is wiped out from a mass infection.[16] Furthermore, in areas with a large population of rats, individual rats can harbor low levels (subclinical) of the plague infection without causing human outbreaks.[15] With no new rat inputs being added to the population from other areas, the infection only spread to humans in very rare cases of overcrowding.[15]
Signs and symptoms
Necrosis of the nose, the lips, and the fingers and residualbruising over both forearms in a person recovering from bubonic plague that disseminated to the blood and the lungs. At one time, the person's entire body wasbruised.
After being transmitted via the bite of an infected flea, theY. pestis bacteria become localized in an inflamedlymph node, where they begin to colonize and reproduce. Infected lymph nodes develop hemorrhages, which result in the death of tissue.[17]Y. pestisbacilli can resist phagocytosis and even reproduce insidephagocytes and kill them. As the disease progresses, the lymph nodes canhemorrhage and become swollen andnecrotic. Bubonic plague can progress to lethalsepticemic plague in some cases. The plague is also known to spread to the lungs and become the disease known as thepneumonic plague. Symptoms appear two to seven days after getting bitten and they include:[14]
Smooth, painful lymph gland swelling called a bubo, commonly found in the groin, but may occur in the armpits or neck, most often near the site of the initial infection (bite or scratch)
Pain may occur in the area before the swelling appears
Gangrene of the extremities such as toes, fingers, lips, and tip of the nose.[18]
The best-known symptom of bubonic plague is one or more infected, enlarged, and painful lymph nodes, known asbuboes. Buboes associated with the bubonic plague are commonly found in the armpits, upper femoral area, groin, and neck region. These buboes will grow and become more painful over time, often to the point of bursting.[19] Symptoms include heavy breathing, continuous vomiting of blood (hematemesis), aching limbs, coughing, and extreme pain caused by the decay or decomposition of the skin while the person is still alive. Additional symptoms include extreme fatigue, gastrointestinal problems, spleen inflammation, lenticulae (black dots scattered throughout the body), delirium,coma, organ failure, and death.[20] Organ failure is a result of the bacteria infecting organs through the bloodstream.[14] Other forms of the disease includesepticemic plague andpneumonic plague, in which the bacterium reproduces in the person's blood and lungs respectively.[21]
Diagnosis
Gram-negativeYersinia pestis bacteria. The culture was grown over a 72-hour time period.
Laboratory testing is required in order todiagnose and confirm plague. Ideally, confirmation is through the identification ofY. pestisculture from a patient sample. Confirmation of infection can be done by examiningserum taken during the early and late stages ofinfection. To quickly screen for theY. pestisantigen in patients, rapiddipstick tests have been developed for field use.[22]
Buboes: Swollen lymph nodes (buboes) characteristic of bubonic plague, a fluid sample can be taken from them with a needle.
Blood:blood cultures test blood samples for bacteria to find source of infection[24]
Lungs:Spirometry test are used to screen the lungs for diseases that affect the airways. Chest X-rays of the lungs are also used as an effective method of diagnosis.[25]
Prevention
Bubonic plague outbreaks are controlled by pest control and modern sanitation techniques. This disease uses fleas commonly found on rats as a vector to jump from animals to humans. The mortality rate is highest in the summer and early fall.[26] The successful control of rat populations in dense urban areas is essential to outbreak prevention. One example is the use of a machine called theSulfurozador, used to deliversulphur dioxide to eradicate the pest that spread the bubonic plague in Buenos Aires, Argentina during the early 18th century.[27] Targetedchemoprophylaxis,sanitation, andvector control also played a role in controlling the 2003Oran outbreak of the bubonic plague.[28] Another means of prevention in large European cities was a city-wide quarantine to not only limit interaction with people who were infected, but also to limit the interaction with the infected rats.[29]
People potentially infected with the plague need immediate treatment and should be given antibiotics within 24 hours of the first symptoms to prevent death. Other treatments include oxygen, intravenous fluids, and respiratory support. People who have had contact with anyone infected by pneumonic plague are given prophylactic antibiotics.[31] Using the broad-based antibiotic streptomycin has proven to be dramatically successful against the bubonic plague within 12 hours of infection.[32]
Globally between 2010 and 2015, there were 3,248 documented cases, which resulted in 584 deaths.[1] The countries with the greatest number of cases are theDemocratic Republic of the Congo,Madagascar, andPeru.[1]
For over a decade since 2001, Zambia, India, Malawi, Algeria, China, Peru, and the Democratic Republic of the Congo had the most plague cases, with over 1,100 cases in the Democratic Republic of the Congo alone. From 1,000 to 2,000 cases are conservatively reported per year to theWHO.[33] From 2012 to 2017, reflecting political unrest and poor hygienic conditions, Madagascar began to host regular epidemics.[33]
Between 1900 and 2015, the United States had 1,036 human plague cases, with an average of 9 cases per year. In 2015, 16 people in the western United States developed plague, including 2 cases inYosemite National Park.[34] These US cases usually occur in rural northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon, and far western Nevada.[35]
In November 2017, the Madagascar Ministry of Health reportedan outbreak to the WHO (World Health Organization) with more cases and deaths than any recent outbreak in the country. Unusually, most of the cases werepneumonic rather than bubonic.[36]
In June 2018, a child was confirmed to be the first person inIdaho to be infected by bubonic plague in nearly 30 years.[37]
A couple died in May 2019, in Mongolia, while huntingmarmots.[38] Another two people in the province of Inner Mongolia, China, were treated in November 2019 for the disease.[39]
Spread of bubonic plague through time in Europe (2nd pandemic)
In July 2020, inBayannur,Inner Mongolia of China, a human case of bubonic plague was reported. Officials responded by activating a city-wide plague-prevention system for the remainder of the year.[40] Also in July 2020, in Mongolia, a teenager died from bubonic plague after consuming infected marmot meat.[41]
History
Yersinia pestis has been discovered in archaeological finds from the Late Bronze Age (~3800BP).[42]Ancient DNA has been used to track the movement of differentvariants of the bacterium across Asia and Europe between 2800–5000 BP, with the bacterial DNA extracted from the teeth of humans who had been infected while alive.[43] Some authors have suggested that the plague was responsible for theNeolithic decline.[44]
The first recorded epidemic affected theSasanian Empire and their arch-rivals, theEastern Roman Empire (Byzantine Empire) and was named thePlague of Justinian (541–549 AD) after emperorJustinian I, who was infected but survived through extensive treatment.[45][46] The pandemic resulted in the deaths of an estimated 25 million (6th century outbreak) to 50 million people (two centuries of recurrence).[47][48] The historianProcopius wrote, in Volume II ofHistory of the Wars, of his personal encounter with the plague and the effect it had on the rising empire.
In the spring of 542, the plague arrived in Constantinople, working its way from port city to port city and spreading around theMediterranean Sea, later migrating inland eastward into Asia Minor and west into Greece and Italy. The Plague of Justinian is said to have been "completed" in the middle of the 8th century.[15] Because the infectious disease spread inland by the transferring of merchandise through Justinian's efforts in acquiring luxurious goods of the time and exporting supplies, his capital became the leading exporter of the bubonic plague. Procopius, in his workSecret History, declared that Justinian was a demon of an emperor who either created the plague himself or was being punished for his sinfulness.[48]
Citizens ofTournai bury plague victims. Miniature fromThe Chronicles ofGilles Li Muisis (1272–1352). Bibliothèque royale de Belgique, MS 13076–77, f. 24v.People who died of bubonic plague in amass grave from 1720 to 1721 inMartigues, France
Medieval society's increasing population was put to deadly halt when, in theLate Middle Ages, Europe experienced the deadliest disease outbreak in history. They called it the Great Dying or The Great Pestilence, later coined The Black Death.[19] Lasting in potency for roughly six years, 1346–1352, the Black Death claimed one-third of the European human population, with mortality rates as high as 70%–80%.[19] Some historians believe that society subsequently became more violent as the mass mortality rate cheapened life and thus increased warfare, crime, popular revolt, waves offlagellants, and persecution.[49] The Black Death originated in Central Asia and spread from Italy and then throughout other European countries. Arab historians Ibn Al-Wardni and Almaqrizi believed the Black Death originated in Mongolia. Chinese records also show a huge outbreak inMongolia in the early 1330s.[50]
In 2022, researchers presented evidence that the plague originated near LakeIssyk-Kul inKyrgyzstan.[51] The Mongols had cut the trade route (theSilk Road) between China and Europe, which halted the spread of the Black Death from eastern Russia to Western Europe. The European epidemic may have begun with thesiege of Caffa, an attack thatMongols launched on the Italian merchants' last trading station in the region,Caffa, in theCrimea.[32]
In late 1346, plague broke out among thebesiegers and from them penetrated the town. The Mongol forces catapulted plague-infested corpses into Caffa as a form of attack, one of the first known instances ofbiological warfare.[52] When spring arrived, the Italian merchants fled on their ships, unknowingly carrying the Black Death. Carried by the fleas on rats, the plague initially spread to humans near the Black Sea and then outwards to the rest of Europe as a result of people fleeing from one area to another. Rats migrated with humans, traveling among grain bags, clothing, ships, wagons, and grain husks.[20] Continued research indicates thatblack rats, those that primarily transmitted the disease, prefer grain as a primary meal.[15] Due to this, the major bulk grain fleets that transported major city's food shipments from Africa andAlexandria to heavily populated areas, and were then unloaded by hand, played a role in increasing the transmission effectiveness of the plague.[15]
The plague resurfaced for a third time in the mid-19th century; this is also known as "the modern pandemic". Like the two previous outbreaks, this one also originated inEastern Asia, most likely inYunnan, a province of China, where there are severalnatural plague foci.[53] The initialoutbreaks occurred in the second half of the 18th century.[54][55] The disease remained localized inSouthwest China for several years before spreading. In the city ofCanton, beginning in January 1894, the disease had killed 80,000 people by June. Daily water traffic with the nearby city ofHong Kong rapidly spread the plague there, killing over 2,400 within two months during the1894 Hong Kong plague.[56]
The third pandemic spread the disease to port cities throughout the world in the second half of the 19th century and the early 20th century via shipping routes.[57] The plague infected people inChinatown in San Francisco from 1900 to 1904,[58] and in the nearby locales ofOakland and theEast Bay again from 1907 to 1909.[59] During the former outbreak, in 1902, authorities made permanent theChinese Exclusion Act, a law originally signed into existence by PresidentChester A. Arthur in 1882. The Act was supposed to last for 10 years, but was renewed in 1892 with theGeary Act, then followed by the 1902 decision. The last major outbreak in the United States occurred in Los Angeles in 1924,[60] though the disease is still present in wild rodents and can be passed to humans who come in contact with them.[35] According to theWorld Health Organization, the pandemic was considered active until 1959, when worldwide casualties dropped to 200 per year. In 1994, aplague outbreak in five Indian states caused an estimated 700 infections (including 52 deaths) and triggered a large migration of Indians within India as they tried to avoid the disease.[citation needed]
It was during the 1894 Hong Kong plague outbreak thatAlexandre Yersin isolated the bacterium responsible (Yersinia pestis),[61] a few days after Japanese bacteriologistKitasato Shibasaburō had isolated it.[62][63] However, the latter's description was imprecise and also expressed doubts of its relation to the disease, and thus the bacterium is today only named after Yersin.[63][64]
Contemporary engraving ofMarseille during theGreat Plague in 1720Copperengraving of aplague doctor from the 17th century. This is one of the most well-known representations in art of the bubonic plague
The scale of death and social upheaval associated with plague outbreaks has made the topic prominent in many historical and fictional accounts since the disease was first recognized. TheBlack Death in particular is described and referenced innumerous contemporary sources, some of which, including works byChaucer,Boccaccio, andPetrarch, are considered part of theWestern canon.The Decameron, by Boccaccio, is notable for its use of aframe story involving individuals who have fled Florence for a secluded villa to escape the Black Death. First-person, sometimes sensationalized or fictionalized, accounts of living through plague years have also been popular across centuries and cultures. For example,Samuel Pepys's diary makes several references to his first-hand experiences of theGreat Plague of London in 1665–66.[65]
Later works, such asAlbert Camus's novelThe Plague orIngmar Bergman's filmThe Seventh Seal have used bubonic plague in settings, such as quarantined cities in either medieval or modern times, as a backdrop to explore themes including the breakdown of society, institutions, and individuals during the plague; the cultural and psychologicalexistential confrontation with mortality; and the plague as an allegory raising contemporary moral or spiritual questions.[citation needed]
Biological warfare
Some of the earliest instances of biological warfare were said to have been products of the plague, as armies of the 14th century were recorded catapulting diseased corpses over the walls of towns and villages to spread the pestilence. This was done byJani Beg when he attacked the city ofKaffa in 1343.[66]
Substantial research has been done regarding the origin of the plague and how it traveled through the continent.[15]Mitochondrial DNA of modern rats in Western Europe indicated that these rats came from two different areas, one being Africa and the other unclear.[15] The research regarding this pandemic has greatly increased with technology.[15] Through archaeo-molecular investigation, researchers have discovered the DNA of plague bacillus in the dental core of those that fell ill to the plague.[15] Analysis of teeth of the deceased allows researchers to further understand both the demographics and mortuary patterns of the disease. For example, in 2013 in England, archeologists uncovered a burial mound to reveal 17 bodies, mainly children, who had died of the Bubonic plague. They analyzed these burial remains usingradiocarbon dating to determine they were from the 1530s, and dental core analysis revealed the presence of Yersinia pestis.[68]
Other evidence for rats that are currently still being researched consists of gnaw marks on bones, predatorpellets and rat remains that were preserved insitu.[15] This research allows individuals to trace early rat remains to track the path traveled and in turn connect the impact of the Bubonic Plague to specific breeds of rats.[15] Burial sites, known as plague pits, offer archaeologists an opportunity to study the remains of people who died from the plague.[69]
Another research study indicates that these separate pandemics were all interconnected.[16] A current computer model indicates that the disease did not go away between these pandemics.[16] It rather lurked within the rat population for years without causing human epidemics.[16]
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^Nicholas Wade (31 October 2010)."Europe's Plagues Came From China, Study Finds".The New York Times.Archived from the original on 4 November 2010. Retrieved1 November 2010.The great waves of plague that twice devastated Europe and changed the course of history had their origins in China, a team of medical geneticists reported Sunday, as did a third plague outbreak that struck less harmfully in the 19th century.
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