Plague (disease)

Plague redirects here. If you are looking for plagues in general, see disease, infectious disease, or epidemic.

Bubonic plague is an infectious disease that is believed to have caused several epidemics or pandemics throughout history.

Infection

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 occurs when people come into contact with infected rodents.

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 blohjhjhjod.

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 infect the bloodstream (septicemic plague) and then 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 gentamycin), 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.

As a biological weapon aerosolized pneumonic plague is the only effective plague agent.

"Doktor Schnabel von Rom" (English: "Doctor Beak from Rome") engraving by Paul Fürst (after J Columbina)

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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 Eastern 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 cases of plague every year.

In Literature

• The Decameron by Giovanni Boccaccio. Takes place in Florence in 1439, during the outbreak of the "Black Death", widely believed to be Bubonic Plague.
• The Plague by Albert Camus. An existentialist novel centered around an outbreak of the plague.
• A Journal of the Plague Year by Daniel Defoe. A first hand account of the bubonic plague outbreak in London