Bubonic plague
- Plague redirects here. If you are looking for plagues in general, see disease, infectious disease, or epidemic.
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2 Symptoms and treatment 3 Historic outbreaks 4 Contemporary cases 5 In Literature |
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 blood.
Symptoms and treatment
The disease becomes evident 2-6 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 FÃÂürst (after J Columbina)
Historic outbreaks
A special warning has to be made about early epidemics of the "plague", for example in Greek or Roman history or in the Bible - these are usually not well enough documented to make any definite statement about the nature of the disease; the usage of the name stems from the early modern time, when the plague was the only disease known to cause massively killing epidemics.
Many scientists believe that there was an outbreak of bubonic plague in the 6th century, starting in Africa and moving to Constantinople and the rest of the Byzantine Empire.
Most scientists believe that the Black Death in the 14th century was an outbreak of bubonic plague. However, other theories have now been advanced, suggesting that the Black Death may have been an outbreak of some other disease, possibly a hemorrhagic fever similar to Ebola. However, the origin of the Black Death epidemic in central Asia, where a particularly virulent strain of plague occurs in the wild marmot population, does suggest it was bubonic plague.
The Great Plague of 1665 in London is also generally believed to have been an outbreak of bubonic plague. This outbreak of Bubonic plague spread across England. Market Stones were set up at approach roads to many towns so that money and goods could be traded without the risk of spreading the disease.
After a localised outbreak in Provence in southern France in 1720-1721, Europe suffered no more such attacks of plague, though the disease remained virulent in other regions, killing upwards of ten million in India in the late nineteenth and early twentieth centuries according to some estimates.
The last rat-borne epidemic in the United States occurred in Los Angeles, California in 1924-1925. The cessation of rat-borne epidemics in most temperate areas is largely related to the ousting of the plague-prone black rat by the larger and more aggressive brown rat. This species is more scrupulous about its hygiene and does not harbour fleas to the extent the black rat does, so greatly reducing the likelihood of infection. Black rats are still widespread in some urban areas in the tropics, and outbreaks may still occur here, as in Gujarat in India in 1994.
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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