In sociology and psychology, mass hysteria is a phenomenon that transmits collective illusions of threats, whether real or imaginary, through a population and society as a result of rumors and fear. In medicine, the term is used to describe the spontaneous manifestation—or production of chemicals in the body—of the same or similar hysterical physical symptoms by more than one person. A common type of mass hysteria occurs when a group of people believes that they have a similar disease or ailment, sometimes referred to as mass sociogenic illness or epidemic hysteria. Middle Ages According to an account which was written by an author in 1784, a nun who lived in a German convent in the 1400s began to bite her companions, and the behavior soon spread through other convents in Germany, Holland and Italy. In The Epidemics of the Middle Ages, an 1844 collection of works written by J. F. C. Hecker (and translated by Benjamin Guy Babington), a translator's note by Babington, citing an unnamed medical textbook, recalls the story of a nun who lived in a French convent during an unspecified time (presumably in the Middle Ages) who inexplicably began to meow like a cat, shortly leading the other nuns in the convent to meow as well. Eventually, all of the nuns in the convent would meow together for a certain period, leaving the surrounding community astonished. This did not stop until the police threatened to whip the nuns. 1500–1800 Witch trials in the early modern period from 1450 to 1750 and especially from 1580 to 1630. Dancing plague of 1518 – a case of dancing mania that occurred in Strasbourg, Alsace (then part of the Holy Roman Empire) in July 1518 wherein numerous people took to dancing for days. Irish Fright (1688) – In England and parts of Wales in December 1688 during the Glorious Revolution, false reports that Irish soldiers were burning and massacring English towns prompted a mass panic in at least 19 counties, with thousands of people arming themselves and preparing to resist non-existent groups of marauding Irishmen. Salem witch trials (1692−1693) – In colonial Massachusetts, adolescent girls Abigail Williams, Betty Parris, Ann Putnam Jr., and Elizabeth Hubbard began to have fits that were described by a minister as "beyond the power of epileptic fits or natural disease to effect." The events resulted in the Salem witch trials, a series of hearings which resulted