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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 does in fact refer 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. While in Europe, people found the disease most occurring in the autumn. Because the plague killed so many of the working population, wages rose and 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), which become swollen and painful and are known as buboes. 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.
Due to its bite-based form of infection, the bubonic plague is often the first step 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.
Two other types of Y. pestis plague are pneumonic and septicemic. Pneumonic plague, unlike the bubonic or septicemic, induces coughing and is very infectious, allowing it to be spread person to person.
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 that origins of the Black Death started off in Mongolia. Later, it was proven that their thesis was correct, as Chinese records showed that the disease made 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 of prevention methods for avoiding the Black Death. One of the most famous ideas 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. Since the people didn't have the knowledge to understand the plague, people believed the plague to be a punishment from God. 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" near it.
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.
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 next few centuries were marked by several local outbreaks of lesser severity. The Great Plague of Seville (1647), the Great Plague of London (1665–1666), the Great Plague of Vienna (1679), Great Plague of Riga (1710) and the Great Plague of Marseille (1720), were the last major outbreaks of the bubonic plague in Europe.
The plague resurfaced in the mid-19th century; like the Black Death, the Third Pandemic began in Central Asia. The disease killed millions in China and India—mostly a British possession at the time—and then spread worldwide. The outbreak continued into the early 20th century. In 1897, the city of Poona (now Pune) in India was severely affected by the outbreak.
In 1899, the islands of Hawaii were also hit by the plague. 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.
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.
In July 2013, following routine testing in and near Los Angeles, CA., health officials publicly confirmed that a squirrel had tested positive with bubonic plague in the Angeles National Forest near Wrightwood. As a precaution, portions of the area have been closed to camping. However, pedestrian traffic through the area continues. Hikers are advised to use insect repellent and ensure that any pets they may bring wear a flea collar.
In December 2013 there was an outbreak of the Bubonic Plague in a village in Madagascar.
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.
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