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Bubonic plague is a zoonotic disease, circulating mainly in fleas on small rodents, and is one of three types of bacterial infections caused by Yersinia pestis (formerly known as Pasteurella pestis), that belongs to the family Enterobacteriaceae. Without treatment, the bubonic plague kills about two thirds of infected humans within four days.
The term bubonic plague is derived from the Greek word βουβών, meaning "groin". Swollen lymph nodes (buboes) especially occur in the armpit and groin in persons suffering from bubonic plague. Bubonic plague was often used synonymously for plague, but it refers specifically to an infection that enters through the skin and travels through the lymphatics, as is often seen in flea-borne infections.
Bubonic plague—along with the septicemic plague and the pneumonic plague, which are the two other manifestations of Y. pestis—is commonly believed to be the cause of the Black Death that swept through Europe in the 14th century and killed an estimated 25 million people, or 30–60% of the European population. Around the Mediterranean Region, summers seemed to be the season when the disease took place. In northern Europe, the disease had its most frequent outbreaks in the autumn. Because the plague killed so many of the working population, wages rose with the demand for labor. Some historians have seen this as a turning point in European economic development.
The most infamous symptom of bubonic plague is an infection of the lymph glands (lymphadenitis), known as buboes, which become swollen and painful. After being transmitted via the bite of an infected flea, the Y. pestis bacteria become localized in an inflamed lymph node, where they begin to colonize and reproduce. Buboes associated with the bubonic plague are commonly found in the armpits, upper femoral, groin and neck region. Acral gangrene (i.e., of the fingers, toes, lips and nose) is another common symptom.
Because of its bite-based mode of transmission, the bubonic plague is often the first of a progressive series of illnesses. Bubonic plague symptoms appear suddenly, usually 2–5 days after exposure to the bacteria. Symptoms include:
Other symptoms include heavy breathing, continuous vomiting of blood (hematemesis), aching limbs, coughing, and extreme pain. The pain is usually caused by the decay or decomposition of the skin while the person is still alive. Additional symptoms include extreme fatigue, gastrointestinal problems, lenticulae (black dots scattered throughout the body), delirium, and coma.
Bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea, Xenopsylla cheopis (the rat flea). In very rare circumstances, as in the septicemic plague, the disease can be transmitted by direct contact with infected tissue or exposure to the cough of another human. The fleas are often found on rodents such as rats and mice, and seek out other prey when their rodent hosts die. The bacteria began its life harmlessly living in the digestive tracts of mammals. The ability to propagate was dependent only upon its ability to travel from mammal host to mammal host. The bacteria remained harmless to the flea, allowing the new host to spread the bacteria. 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, bacteria rapidly spread to the lymph nodes and multiply.
Y. pestis bacilli can resist phagocytosis and even reproduce inside phagocytes and kill them. As the disease progresses, the lymph nodes can haemorrhage and become swollen and necrotic. Bubonic plague can progress to lethal septicemic plague in some cases. The plague is also known to spread to the lungs and become the disease known as the pneumonic plague. This form of the disease is highly communicable as the bacteria can be transmitted in droplets emitted when coughing or sneezing.
Laboratory testing is required in order to diagnose and confirm plague. Ideally, confirmation is through the identification of Y. pestis culture from a patient sample. Confirmation of infection can be done by examining serum taken during the early and late stages of infection. To quickly screen for the Y. pestis antigen in patients, rapid dipstick tests have been developed for field use.
Several classes of antibiotics are effective in treating bubonic plague. These include aminoglycosides such as streptomycin and gentamicin, tetracyclines (especially doxycycline), and the fluoroquinolone ciprofloxacin. Mortality associated with treated cases of bubonic plague is about 1–15%, compared to a mortality of 40–60% in untreated cases.
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. Using the broad-based antibiotic streptomycin has proven to be dramatically successful against the bubonic plague within 12 hours of infection.
The first recorded epidemic ravaged the Byzantine Empire during the sixth century, and was named the Plague of Justinian after emperor Justinian I, who was infected but survived through extensive treatment. The epidemic is estimated to have killed approximately 50 million people in the Roman Empire alone. The historian Procopius wrote, in Volume II of History of the Wars, his 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 through the Mediterranean, later migrating inland eastward into Asia Minor and west into Greece and Italy. 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 work Secret History, declared that Justinian was a demon of an emperor who either created the plague himself or was being punished for his sinfulness.
In the Late Middle Ages (1340–1400) Europe experienced the most deadly disease outbreak in history when the Black Death, the infamous pandemic of bubonic plague, hit in 1347, killing a third of the human population. It is believed that society subsequently became more violent as the mass mortality rate cheapened life and thus increased warfare, crime, popular revolt, waves of flagellants, and persecution. The Black Death originated in or near China and spread from Italy and then throughout other European countries. Arab historians Ibn Al-Wardni and Almaqrizi believed the Black Death originated in Mongolia, and this was proven correct as Chinese records showed a huge outbreak in Mongolia in the early 1330s. Research published in 2002 suggests that it began in the spring of 1346 in the steppe region, where a plague reservoir stretches from the northwestern shore of the Caspian Sea into southern Russia. The Mongols had cut off the trade route, the Silk Road, between China and Europe which halted the spread of the Black Death from eastern Russia to Western Europe. The epidemic began with an attack that Mongols launched on the Italian merchant's last trading station in the region, Caffa in the Crimea. In the autumn of 1346, plague broke out among the besiegers and from them penetrated into the town. 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.
There were many ethno-medical beliefs for avoiding the Black Death. One of the most famous was that by walking around with flowers in or around their nose people would be able to "ward off the stench and perhaps the evil that afflicted them". People believed the plague to be a punishment from God, and that the only way to be rid of the plague was to be forgiven by God. One such method used was to carve the symbol of the cross onto the front door of a house with the words "Lord have mercy on us".
Pistoia, a city in Italy, even went as far as enacting rules and regulations on the city and its inhabitants to keep it safe from the Black Death. The rules stated that no one was allowed to visit any plague-infected area and if they did they were not allowed back into the city. Some other rules were that no linen or woollen goods were to be imported into the city and no corpses were to be buried in the city. However, despite strict enforcement of the rules, the city eventually became infected. People who weren't infected with the plague gathered in groups and stayed away from the sick. They ate and drank with limited food and water and weren't even allowed oral communication because merely talking with one another increased the chance of passing on the disease.
While Europe was devastated by the disease, the rest of the world fared much better. In India, populations rose from a population of 91 million in 1300, to 97 million in 1400, to 105 million in 1500. Also sub-Saharan Africa remained largely unaffected by the plagues.
The next few centuries were marked by several localized or regional outbreaks of lesser severity. The Great Plague of Seville (1647), the Great Plague of London (1665-1666), the Great Plague of Vienna (1679), Great Baltic plague (1708-1712.) and the Great Plague of Marseille (1720), were the last major outbreaks of the bubonic plague in Europe.
Medieval doctors thought the plague was created by air corrupted by humid weather, decaying unburied bodies, and fumes produced by poor sanitation. The recommended treatment of the plague was a good diet, rest, and relocating to a non-infected environment so the individual could get access to clean air. This did help, but not for the reasons the doctors of the time thought. In actuality, because they recommended moving away from unsanitary conditions, people were, in effect, getting away from the rodents that harbored the fleas carrying the infection. However, this also helped to spread the infection to new areas previously non-infected.
The plague resurfaced for a third time in the mid-19th century. Like the two previous outbreaks, this one also originated in Eastern Asia. The initial outbreak occurred in China's Yunnan province in 1855. The disease remained localized in Southwest China for several years before spreading. In the city of Canton, beginning in March 1894, the disease killed 60,000 people in a few weeks. Daily water-traffic with the nearby city of Hong Kong rapidly spread the plague there, killing over 100,000 within two months.
From China, the plague spread to the Indian subcontinent around 1896. Over the next thirty years, India would lose 12.5 million people to the Bubonic plague. The disease was initially seen in port cities, beginning with Bombay (now Mumbai), but later emerged in Poona (now Pune), Kolkata, and Karachi (now in Pakistan). By 1899, the outbreak spread to smaller communities and rural areas in many regions of India. Overall, the impact of plague epidemics was greatest in western and northern India—in the provinces then designated as Bombay, Punjab, and the United Provinces—while eastern and southern India were not as badly affected. Ultimately, more than 12 million people died from the plague in India (including present day Pakistan and Bangladesh) and China alone.
In 1899, the plague reached the islands of Hawaii. The first evidence of the disease was found in Honolulu's Chinatown on Oahu. It was located very close to the island's piers, and rats in cargo ships from China were able to land on the Hawaiian islands unseen. As the rats, hosts for disease-carrying fleas, made their way deeper into the city, people started to fall ill. On December 12, 1899, the first case was confirmed. The Board of Health then quickly thought of ways to prevent the disease from spreading even further inland. Their solution was to burn down any buildings in Chinatown suspected of containing a source of the disease. On December 31, 1899, the board set the first fire. They had originally planned to burn only a few targeted buildings, and thought they could control the flames as each building was finished, but the fire got out of control, burning down untargeted neighboring buildings. The resulting fire caused many of Chinatown's homes to be destroyed and an estimated 4,000 people were left homeless.
Australia suffered 12 major plague outbreaks between 1900 and 1925 originating from shipping. Research by Australian medical officers Thompson, Armstrong and Tidswell contributed to understanding the spread of Yersinia pestis to humans by fleas from infected rats.
According to the World Health Organization, the pandemic was considered active until 1959, when worldwide casualties dropped to 200 per year. In 1994, a plague 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 plague.
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.
Later, plague was used during the Second Sino-Japanese War as a bacteriological weapon by the Imperial Japanese Army. These weapons were provided by Shirō Ishii's units and used in experiments on humans before being used on the field. For example, in 1940, the Imperial Japanese Army Air Service bombed Ningbo with fleas carrying the bubonic plague. During the Khabarovsk War Crime Trials, the accused, such as Major General Kiyashi Kawashima, testified that, in 1941, some 40 members of Unit 731 air-dropped plague-contaminated fleas on Changde. These operations caused epidemic plague outbreaks.
We confirm that Y. pestis caused the Black Death and later epidemics on the entire European continent over the course of four centuries. Furthermore, on the basis of 17 single nucleotide polymorphisms plus the absence of a deletion in glpD gene, our aDNA results identified two previously unknown but related clades of Y. pestis associated with distinct medieval mass graves. These findings suggest that plague was imported to Europe on two or more occasions, each following a distinct route. These two clades are ancestral to modern isolates of Y. pestis biovars Orientalis and Medievalis. Our results clarify the etiology of the Black Death and provide a paradigm for a detailed historical reconstruction of the infection routes followed by this disease.
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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