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Buboes on a plague patient, courtesy CDC, via Wikipedia

Bubonic plague is a disease that affects several species including humans. It circulates mainly among small rodents such as rats, and their fleas and is one of three types of bacterial infections caused by Yersinia pestis (formerly known as Pasteurella pestis), which belongs to the family Enterobacteriaceae. Without treatment, the bubonic plague kills about two thirds of infected humans within 4 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 lymphatic system, 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 Yersinia pestis—is generally 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. 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.

Yersinia pestis, the bacteria that causes plague. These were stained with a fluorescent die (courtesy CDC)

Signs and symptoms

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. Gangrene of the fingers, toes, lips and nose is another common symptom.

Gangrene and necrosis of the extremities in a plague patient. The dark color gave the disease it's nickname as the "Black Death" as the necrosis spread through the body

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:

  • Acral gangrene: Gangrene of the extremities such as toes, fingers, lips and tip of the nose.
  • Chills
  • Malaise
  • High fever (39 °Celsius; 102 °Fahrenheit)
  • Muscle cramps
  • Seizures
  • Smooth, painful lymph gland swelling called a buboe, commonly found in the groin, but may occur in the armpits or neck, most often at the site of the initial infection (bite or scratch)
  • Pain may occur in the area before the swelling appears
  • Skin color changes to a pink hue in some very extreme cases

Other symptoms include heavy breathing, continuous vomiting of blood, 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.


The oriental rat flea, both magnified to show it's gut, and actual size. The bacteria that causes plague lives in the flea's gut and is transmitted when it bites.

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.

The black rat, one of the most common vectors of the disease. Black rat numbers were also reduced by the plague, and it was largely replaced by the brown rat, which is less likely to carry the disease.

Yersinia pestis bacilli can resist being devoured by the cells of the body’s immune system and even reproduce inside white blood cells and kill them. As the disease progresses, the lymph nodes can start bleeding 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.


A 1650's drawing of a plague doctor. The mask has small breathing holes and contains either smoke or perfume to ward off the "bad smells" or "miasma" associated with plague infection. The costume was effective, but only because the thick leather coat was effective against flea bites.

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 rate 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.

Although plague vaccines are in development, none of them have been proven to be effective in practice.  

Laboratory testing

Laboratory testing is required in order to diagnose and confirm plague. Ideally, confirmation is through the identification of Y. pestis blood culture from a patient sample. Confirmation of infection can be done by examining blood 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.


Early outbreaks

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.

Black Death

This contemporary illustration from the 1411 Toggeburg bible depicts some of the symptoms of smallpox, but the buboes point to plague and it is now believed the disease that swept through the town in that year was plague.

In the Late Middle Ages (1340-1400) Europe experienced the most deadly disease outbreak in Western history when the Black Death, the infamous pandemic of bubonic plague, hit in 1347, killing a third of the human population. It is commonly 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. Research published in 2002 suggests that it began in the spring of 1346 in the steppe region, where a plague reservoir stretches from the north-western 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.

Although Shakespeare escaped the Black Death, his career was put on hold during an outbreak that closed theaters from 1592-1593

Due to their association with witchcraft, cats were not tolerated during plague outbreaks, which actually allowed rats to spread more readily.

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." There were also many religious prevention methods. 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.

The spread of plague was poorly understood and resulted in many measures that were either harsh and useless or actually increased the spread of the disease. In this contemporary illustration, Jews are being burned alive as it was believed they spread the disease.

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 woolen 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. 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 and Scandinavia remained largely unaffected by the plagues.

A map of the spread of the plague through Europe

Traditional treatment

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.

Later outbreaks

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 Marseilles (1720), were the last major outbreaks of the bubonic plague in Europe.

A contemporary drawing showing the removal of bodies during the 1665 outbreak in London. This outbreak caused about 100,000 casualties.

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 un-targeted 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 John Ashburton Thompson, Armstrong and Frank Tidswell contributed to understanding the spread of Yersinia pestis to humans by fleas from infected rats.

Victims of a plague outbreak in Manchuria in 1910-1911

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 1994 and 2010 cases were reported in Peru.

In 2012, cases were reported in Oregon and Colorado, including a 7-year-old girl who contracted Bubonic plague while camping in southwest Colorado.

In September 2012 a herdsman in China (Sichuan province, Garzê Tibetan Autonomous Prefecture) was reported to have died of the disease after finding a dead marmot and eating it.

A 1998 diagram showing the locations where plague remains endemic, if rare

Biological warfare

Some of the earliest instances of biological warfare were said to have been product of the plague, as armies of the 14th century were recorded catapulting diseased corpses over the walls of towns and villages in order 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.

On the series

Hannah in Sleeping Dogs Lie

Three Stories was the first time plague was mentioned:

"I know you're not too busy. You avoid work like the plague. Unless it is the plague"
Stacy Warner

Plague has only been mentioned on the show in one other context - in the Season 2 episode Sleeping Dogs Lie, where it was the final diagnosis of Hannah.

Hannah's case first presented with severe insomnia, punctuated by short periods of sleep - a very unusual presentation.  The team had to rule out rectal tumorgranulomatosis with polyangiitisWilson's disease, and mushroom poisoning.

House finally realized the possibility of plague when he realized she had been in contact with a dog that had been to the Southwest, where the disease is still found in wild animals.  He checked for buboes under her armpits and found them.

There is also one other oblique reference in the series - St. Sebastian's Hospital, another fictional hospital in the Princeton area, is named for patron saint for the deliverance from plague.  


Plague at NIH

Bubonic plague at Wikipedia (this article was largely developed from Wikipedia's article on the subject)

Plague at Mayo Clinic

Plague at the World Health Organization

Plague at the Centers for Disease Control

The Plague at the Public Health Agency of Canada

Plague at



The Black Death - Professor Sir Richard J. Evans FBA


The Mystery of The Black Death


Girl survives bubonic plague in Colorado, USA


The Black Death - Worst plague in history

From The History Channel


Bubonic Plague - Monsters Inside Me Ep6


The Black Death Documentary

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