In the 14th century, the Jews of northern Europe—who had already suffered from massacres during the crusades and wholesale expulsion from England in 1290—faced a new problem: they were accused of spreading disease among Christians by poisoning the wells. Tzafrir Barzilay suggests that this libel began with rumors that lepers were deliberately spreading their condition through the water supply, which in turn gave rise to similar accusations against Jews:
In France the allegations convinced officials and rulers to change course and move from defending minority groups to acting against them. The accusations were a phenomenon unique to the later Middle Ages, appearing, flourishing, and declining during a single century.
Toward late June , a month before the king ordered their arrest, such rumors triggered violence against Jews in the county of Anjou. Count Philip of Valois (later King Philip VI) described the events in a letter sent to Pope John XXII shortly afterward. He wrote that June 26, 1321 was an ominous day; a major solar eclipse was seen in Anjou and Touraine, turning the sun red as blood. This report is corroborated by other sources and astronomical data. Philip, who apparently accepted the eclipse as an apocalyptic sign, added that thunderstorms and earthquakes struck, fire rained down from the sky, and even a dragon flew through the air and killed many with its foul breath. He stated that “the inhabitants of the land believed that the end of the world had just come.”
In their panic, the people of Anjou suspected that local Jews had something to do with these ominous signs: “On the next day [June 27], in the said county [Anjou], our people began to attack Jews, because of sorcery that they performed against Christianity.” These suspicions may have been related to well-poisoning accusations, which were already widespread in the Touraine, close to Anjou. However, Philip insists that evidence for Jewish involvement in the plot was found only when suspicious Christians “examined carefully the houses of specific Jews,” probably in search of signs of sorcery.