One can hardly imagine anything more horrible than plague destroying whole cities. Our ancestors feared the disease more than war, identifying it with death.

Plague: Causative Agent and Signs of Disease

The disease provokes the plague bacillus (lat. Yersinia pestis), discovered in 1894 by French scientist A. E. J. Yersin (1863-1943) and Japanese scientist S. Kitasato (1852-1931).

Plague manifests itself in a severe general state of health, fever, swelling of the lymph nodes, lungs and other internal organs. The disease is extremely contagious, it belongs to the group of the quarantine infections, it has a high mortality rate.

The incubation period lasts from several hours to 3-6 days. There is a fever, increased heart rate, the lower blood pressure; the temperature rises sharply to 39ºС. The illness is accompanied by delirium, confusion, loss of coordination.

There are several forms of plague: bubonic, pulmonary, septic, and easy (small plague).

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  • In the bubonic plague the lymph nodes increase, they are inflamed and filled with pus (also called buboes). The liver and spleen can also increase. Without treatment death occurs in 3-5-day, mortality exceeds 60%. There is a possible transition of this form into secondary pneumonic or second-septic form.
  • Pneumonic plague affects the lungs. Its distinctive symptoms include cough, hemoptysis. A fever, headache, palpitations, and heavy breating are also present.
  • Septic form of plague occurs with hemorrhages in the skin, bleeding of the gastrointestinal tract, tachycardia, decrease in the blood pressure. Death comes in one day, sometimes before the signs of bubonic or pneumonic plague appear.
  • Light (small) form of plague can occur in areas endemic for plague. These include: Vietnam, Burma, Bolivia, Ecuador, Turkmenistan, etc., in Russia – Caspian lowland, the East-Ural region, Stavropol, TRANS-Baikal, Altai and some other regions. The symptoms are swollen lymph nodes, a headache, a fever. They usually disappear within a week.

Natural sources of Yersinia Pestis are rodents (rats, mice, hares, gophers, marmots, squirrels), as well as wild dogs, cats and camels. They contract the disease through their bites or from fleas, which are the vectors of the disease.

Another way of transmission is a personal contact and airborne droplets (from an infected person).

The plague microbe is not afraid of low temperatures and freezing, it can remain up to 60 days in bodies of dead animals; however, when using disinfectants and boiling clothes, it dies.

“The Black Death”

Known pandemics of plague in history:

  • “Justiniana plague” in the Eastern Roman Empire (551-580.), killed more than 100 million people;
  • The pandemic of the fourteenth century — the Black Death (1346-1352., 25 million died – a third of Europe’s population);
  • The plague in London (1664-1665, 20% of the population died), Marseilles and some towns of Provence (1720-1722, 100 thousand persons perished) and Moscow (1771-1772, about 57 thousand people perished);
  • At the end of the XIX century the third pandemic began in Asia (more than 12 million people);
  • In the twentieth century the epidemic in India broke out (more than 12.5 thousand victims).


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Such a high mortality in the Middle Ages was due to the lack of proper treatment (cutting and burning plague buboes) and failure to comply with quarantine measures. There are also the data that people infected with plague were used as biological weapons.

Plague Today

Currently in the world about 2.5 thousand patients are registered.

According to World Health Organization, from 1989 to 2004 there were about 40 thousand cases in 24 countries, the mortality rate was about 7%. In Russia since 1979 there have been no cases of the disease, but on the territory of the natural foci, the risk of infection is present for more than 20 thousand people. The situation is complicated by the annual detection of cases in neighboring countries (Mongolia, Kazakhstan, China).

Plague is treated with antibiotics (the first successful treatment was held in 1947 with streptomycin, developed by the Research Institute of Epidemiology and Hygiene of the Red Army), sulfonamides, and anti-plague serum. The patient and people who are in the constant contact with him are isolated (especially during the pneumonic form).

To prevent the spread of plague populations of rodents are always controlled and plague control institutions are created in endemic areas. There is also a vaccine, reducing the severity of the disease, but it does not protect 100%.