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Bubonic plague

The meaning of «bubonic plague»

Bubonic plague is one of three types of plague caused by the plague bacterium (Yersinia pestis).[1] One to seven days after exposure to the bacteria, flu-like symptoms develop.[1] These symptoms include fever, headaches, and vomiting,[1] as well as swollen and painful lymph nodes occurring in the area closest to where the bacteria entered the skin.[2] Occasionally, the swollen lymph nodes, known as "buboes" may break open.[1]

The three types of plague are the result of the route of infection: bubonic plague, septicemic plague, and pneumonic plague.[1] Bubonic plague is mainly spread by infected fleas from small animals.[1] It may also result from exposure to the body fluids from a dead plague-infected animal.[5] Mammals such as rabbits, hares, and some cat species are susceptible to bubonic plague, and typically die upon contraction.[6] In the bubonic form of plague, the bacteria enter through the skin through a flea bite and travel via the lymphatic vessels to a lymph node, causing it to swell.[1] Diagnosis is made by finding the bacteria in the blood, sputum, or fluid from lymph nodes.[1]

Prevention is through public health measures such as not handling dead animals in areas where plague is common.[7][1] Vaccines have not been found to be very useful for plague prevention.[1] Several antibiotics are effective for treatment, including streptomycin, gentamicin, and doxycycline.[3][4] Without treatment, plague results in the death of 30% to 90% of those infected.[1][3] Death, if it occurs, is typically within 10 days.[8] With treatment, the risk of death is around 10%.[3] 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 the Democratic Republic of the Congo, Madagascar, and Peru.[1]

The plague was the cause of the Black Death that swept through Asia, Europe, and Africa in the 14th century and killed an estimated 50 million people,[1][9] including about 25% to 60% of the European population.[1][10] Because the plague killed so many of the working population, wages rose due to the demand for labor.[10] Some historians see this as a turning point in European economic development.[10] The disease was also responsible for the Plague of Justinian, originating in the Eastern Roman Empire in the 6th century CE, as well as the third epidemic, affecting China, Mongolia, and India, originating in the Yunnan Province in 1855.[11] The term bubonic is derived from the Greek word βουβών, meaning "groin".[12]

Bubonic plague is an infection of the lymphatic system, usually resulting from the bite of an infected flea, Xenopsylla cheopis (the Oriental rat flea).[13] Several flea species carried the bubonic plague, such as Pulex irritans (the human flea), Xenopsylla cheopis, and Ceratophyllus fasciatus.[13] Xenopsylla cheopis was the most effective flea species for transmittal.[13] In very rare circumstances, as in septicemic plague, the disease can be transmitted by direct contact with infected tissue or exposure to the cough of another human. The flea is parasitic on house and field rats and seeks out other prey when its rodent hosts die. The bacteria remain harmless to the flea, allowing the new host to spread the bacteria. Rats were an amplifying factor to bubonic plague due to their common association with humans as well as the nature of their blood.[14] The rat's blood allowed the rat to withstand a major concentration of the plague.[14] 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. The fleas that transmit the disease only directly infect humans when the rat population in the area is wiped out from a mass infection.[15] Furthermore, in areas of a large population of rats, the animals can harbor low levels of the plague infection without causing human outbreaks.[14] With no new rat inputs being added to the population from other areas, the infection would only spread to humans in very rare cases of overcrowding.[14]

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