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Plague has been known for at least 3000 years. Epidemics have been
recorded in China since 224 BC. The disease occurred in huge pandemics that
destroyed the entire populations of cities throughout the Middle Ages; they have
occurred sporadically since that time. The last great pandemic began in China in 1894
and spread to Africa, the Pacific islands, Australia, and the Americas, reaching San
Francisco in 1900. Plague still occurs in Asia, Africa, South America, and Australia,
but rarely appears in the U.S. Two small, well-contained outbreaks occured in India in
1994. In 1950 the World Health Organization initiated sanitation programs for plague
control throughout the world.
Bubonic plague is an acute infection in humans and various species of rodents,
caused by Yersinia pestis (formerly called Pasteurella pestis), a bacterium trans-
mitted by fleas that have fed on the blood of infected rodents, usually rats. The
ingested plague bacteria multiply in the flea\'s upper digestive tract and even-
tually obstruct it. When the flea feeds again on a human or another rodent, the
obstruction causes the freshly ingested blood to be regurgitated back into the bite,
along with the plague bacteia. The circulatory system of the bitten individual then
carries the bacteria throughout the body.
The first signs of illness in humans appear suddenly, within about a week. In a few
hours the body temperature rises to about 40 degrees C(104 degrees F), and the vic-
tim becomes gravely ill, experiencing vomiting, muscular pain, mental disorganiza-
tion, and delirium. The lymph nodes throughout the body, especially those in the
groin and the thighs, become enlarged and extremely painful. The inflamed lymph
nodes, called buboes(from which the disease gets its name), become filled with pus,
and the disease spreads through the body by way of the infected bloodstream and
the lymphatic system. In 60-90 percent of untreated cases, death usually occurs with-
in a few days.
Plague pneumonia, or pneumonic plague, is caused by the same bacteria as Bubonic
plague but is acquired by inhaling infected droplets from the lungs of someone whose
plague infection has spread to the respiratory system. This is the most contagious form
of the disease and the form that progresses most rapidly, with death usually occurring in
less than three days in virtually all untreated cases.
The most effective way to prevent plague is to reduce the rodent the flea populations
by the use of proper sanitation and rodenticides and insecticides. The plague organism
is vulnerable to the antibiotics streptomycin, chloramphenicol, and tetracycline, if
treatment is started within about 15 hours of the first appearance of symptoms.
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Plague, Bubonic plague, Yersinia pestis, Pneumonic plague, Flea, Yersinia, Septicemic plague, Bubo, Black Death
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