Bubonic plague is an infectious disease that is believed to have caused several epidemics or pandemics throughout history. Bubonic plague is the most common form of plague which causes swollen, tender inflamed lymph glands (called buboes); other forms are Septicemic plague which occurs when plague bacteria multiply in the blood and Pneumonic plague which occurs when the lungs are infected.

Infection/transportation

It is primarily a disease of rodents, particularly marmots (in which the most virulent strains of plague are primarily found), but also black rats, prairie dogs, chipmunks, squirrels and other similar large rodents. Human infection most often occurs when a person is bitten by a flea that has previously fed on an infected rodent.

In 1896, bacteriologist Alexandre Yersin isolated the responsible bacterium and determined the common mode of transmission. The disease is caused by the bacterium Yersinia pestis and is usually transmitted by the bite of fleas from an infected host, often a black rat. The bacteria are transferred from the blood of infected rats to the rat flea (Xenopsylla cheopsis). The bacillus multiplies in the stomach of the flea, blocking it. When the flea next bites a mammal, the consumed blood is regurgitated along with the bacillus into the bloodstream of the bitten animal. Any serious outbreak of plague is started by other disease outbreaks in the rodent population. During these outbreaks, infected fleas that have lost their normal hosts seek other sources of blood.

Symptoms and treatment

The disease becomes evident 2-7 days after infection. Initial symptoms are chills, fever, headaches, and the formation of buboes. The buboes are formed by the infection of the lymph nodes, which swell and become prominent. If unchecked, the bacteria infects the bloodstream (septicemic plague), which can progress to the lungs (pneumonic plague).

In septicemic plague there is bleeding into the skin and other organs, which creates black patches on the skin, hence the name Black Death. Untreated septicemic plague is universally fatal, but early treatment with antibiotics is effective (usually streptomycin or gentamicin), reducing the mortality rate to around 15% (USA 1980s). People who die from this form of plague often die on the same day that symptoms first appear.

With pneumonic plague the infected lungs raised the possibility of person-to-person transmission through respiratory droplets. The incubation period for pneumonic plague is usually between two to four days, but can be as little as a few hours. The initial symptoms of headache, weakness, and coughing with hemoptysis are indistinguishable from other respiratory illnesses. Without diagnosis and treatment the infection can be fatal in one to six days; mortality in untreated cases may be as high as 95%. The disease can be effectively treated with antibiotics, however.

Plague as a biological weapon

Plague has a long history as a biological weapon. Historical accounts from medieval Europe detail the use of infected animal carcasses, by Mongols, Turks and other groups, to infect enemy water supplies. Plague victims were also reported to have been tossed by catapult into cities under seige.

During World War II, the Japanese Army developed weaponized plague based on the breeding and release of large numbers of fleas. During the Japanese occupation of Manchuria, civilians and prisoners of war were deliberately infected with the plague bacillus. These subjects, called "logs", were then studied by dissection, some while still living and conscious. After World War II, both the United States and the Soviet Union developed means of weaponizing pneumonic plague. Experiments included various delivery methods, vacuum drying, sizing the bacillus, developing strains resistant to antibiotics, combining the bacillus with other diseases, such as diptheria, and genetic engineering. Scientists who worked in USSR bio-weapons programs have stated that the Soviet effort was formidable and that large stocks of weaponized plague bacillus were produced. Information on many of the Soviet projects is largely unavailable. Aerosolized pneumonic plague remains the most significant threat.[1] (http://www.vnh.org/BIOCASU/9.html)[2] (http://www.biohazardnews.net/agent_plague.shtml)

"Doktor Schnabel von Rom" (English: "Doctor Beak from Rome") engraving by Paul Fürst (after J Columbina). The beak is a primitive gas mask, stuffed with substances thought to ward off the plague.

Historical cases

The Plague of Justinian is the first known pandemic on record, and it also marks the first recorded case of bubonic plague in 541. At its peak, the plague was killing 10,000 people in Constantinople every day and perhaps 40 percent of the city's inhabitants. It went on to destroy up to a quarter of the human population of the eastern Mediterranean.

During the mid-1300s, a massive and deadly epidemic swept through Europe, killing one-third of the population by some estimates, and subsequently changing the course of European history. Commonly referred to as The Black Death, many scientists and historians believe that this outbreak was an incidence of bubonic plague.

Bubonic plague struck parts of Europe throughout the 1400s, 1500s and 1600s with varying degrees of intensity and fatality. Researchers still do not agree on why the infection never returned to Europe after that.

The third pandemic began in China in 1855, spread to all inhabited continents, and ultimately killed more than 12 million people in India and China alone!

Contemporary cases

The disease still exists in wild animal populations from the Caucasus Mountains east across southern and central Russia, to Kazakhstan, Mongolia and parts of China; in Southwest and Southeast Asia, Southern and East Africa; and in North America from the Pacific Coast eastward to the western Great Plains, and from British Columbia south to Mexico; and in South America in two areas—the Andes mountains and Brazil. There is no plague-infected animal population in Europe or Australia.

Globally, the World Health Organization reports 1,000 to 3,000 human cases of plague every year.

In literature

• The Decameron by Giovanni Boccaccio (1350). Takes place in Florence in 1348, during the outbreak of the "Black Death", widely believed to be Bubonic Plague.
• The Plague by Albert Camus (1947). An existentialist novel centered around an outbreak of the plague.
• A Journal of the Plague Year by Daniel Defoe (1722). A fictional first hand account of the London outbreak of 1665.
• Doomsday Book by Connie Willis (1992). A Hugo award and Nebula award-winning historical science fiction novel, in which a time-traveler inadvertently ends up in the plague-ridden England of 1348.

See also

• Black Death
• Epidemics
• Medieval demography

External links

• World Health Organization
  • Health topic (http://www.who.int/topics/plague/en/)
  • Communicable Disease Surveillance & Response (http://www.who.int/csr/disease/plague/en/) - Impact of plague & Information resources
• Centers for Disease Control and Prevention
  • CDC Plague (http://www.cdc.gov/ncidod/dvbid/plague/index.htm) map world distribution, publications, information on bioterrorism preparedness and response regarding plague
  • Infectious Disease Information (http://www.cdc.gov/ncidod/diseases/submenus/sub_plague.htm) more links including travelers' health

da:Byldepest de:Pest es:Peste eo:Pesto fr:Peste he:דבר hr:Kuga it:Peste nl:Pest (ziekte) ja:ペスト pl:Czarna śmierć simple:Bubonic plague sl:kuga sv:Pest zh:鼠疫