- 1a : a disastrous evil or affliction : calamity
- b : a destructively numerous influx <a plague of locusts>
- 2a : an epidemic disease causing a high rate of mortality : pestilence
- b : a virulent contagious febrile disease that is caused by a bacterium (Yersinia pestis) and that occurs in bubonic, pneumonic, and septicemic forms —called also black death
- 3a : a cause of irritation : nuisance
- b : a sudden unwelcome outbreak <a plague of burglaries>
Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents (most notably rats) and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death and devastation it brought. Until June 2007, plague was one of only three diseases specifically reportable to the World Health Organization (the two other ones were cholera and yellow fever). Depending on lung infection, or sanitary conditions, plague also can be spread in the air, by direct contact, or by contaminated undercooked food or materials. The symptoms of plague depend on the concentrated areas of infection in each person: such as bubonic plague in lymph nodes, septicemic plague in blood vessels, pneumonic plague in lungs, and so on. Medicines can cure plague if detected early. Plague is still endemic in some parts of the world.