[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.

[6] Mammals such as rabbits, hares, and some cat 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 the lymphatic vessels to a lymph node, causing it to swell.

[1] The plague is considered the likely cause of the Black Death that swept through Asia, Europe, and Africa in the 14th century and killed an estimated 50 million people,[1][10] including about 25% to 60% of the European population.

Rats were an amplifying factor to bubonic plague due to their common association with humans as well as the nature of their blood.

[16] Furthermore, in areas with a large population of rats, the animals can harbor low levels of the plague infection without causing human outbreaks.

[15] 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 area, groin, and neck region.

[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.

One example is the use of a machine called the Sulfurozador, used to deliver sulphur dioxide to eradicate the pest that spread the bubonic plague in Buenos Aires, Argentina during the early 18th century.

[30] People potentially infected with the plague need immediate treatment and should be given antibiotics within 24 hours of the first symptoms to prevent death.

[47][48] The historian Procopius wrote, in Volume II of History of the Wars, of his personal encounter with the plague and the effect it had on the rising empire.

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.

[48] Medieval society's increasing population was put to deadly halt when, in the Late Middle Ages, Europe experienced the deadliest disease outbreak in history.

[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 of flagellants, and persecution.

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.

Like the two previous outbreaks, this one also originated in Eastern Asia, most likely in Yunnan, a province of China, where there are several natural plague foci.

[57] The plague infected people in Chinatown in San Francisco from 1900 to 1904,[58] and in the nearby locales of Oakland and the East Bay again from 1907 to 1909.

[59] During the former outbreak, in 1902, authorities made permanent the Chinese Exclusion Act, a law originally signed into existence by President Chester A. Arthur in 1882.

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.

[63][64] 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.

The Black Death in particular is described and referenced in numerous contemporary sources, some of which, including works by Chaucer, Boccaccio, and Petrarch, are considered part of the Western canon.

The Decameron, by Boccaccio, is notable for its use of a frame story involving individuals who have fled Florence for a secluded villa to escape the Black Death.

[citation needed] 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.

For example, in 1940, the Imperial Japanese Army Air Service bombed Ningbo with fleas carrying the bubonic plague.

[67] During the Khabarovsk War Crime Trials, the accused, such as Major General Kiyoshi Kawashima, testified that, in 1941, 40 members of Unit 731 air-dropped plague-contaminated fleas on Changde.

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 using radiocarbon dating to determine they were from the 1530s, and dental core analysis revealed the presence of Yersinia pestis.