Bubonic plague

Bubonic plague is a contagious pandemic disease caused by the bacterium Yersinia pestis and is usually transmitted by the bite of fleas from an infected host, often a 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.

The infection 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 the bacteria infect the bloodstream (plague septicemia) and then the lungs (plague pneumonia).

In plague septicemia there is bleeding into skin and other organs, which creates black patches on the skin, hence the name Black Death. Mortality in untreated cases is 50-90%, but early treatment with antibiotics is effective (usually streptomycin? or gentamycin?), reducing the mortaltiy rate to around 15% (USA 1980s).

The disease still exists in wild animal populations in the [Caucasus Mountains]? in Russia, through much of the Middle East, China, Southwest and Southeast Asia, Southern and Eastern Africa, in North America from the Pacific Coast eastward to the western [Great Plains]? and from British Columbia southward to Mexico, and in South America in two areas - the the Andean 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. The last rat-borne epidemic in the United States occurred in Los Angeles in 1924-25

Compare [Pneumonic plague]?