Rosh Hashana and the Black Death

We find echoes of the Black Death in Jewish custom and law even today. For instance, Jews have an old custom on the first day of Rosh Hashannah to go to a body of water, recite some prayers and symbolically cast one’s sins into the sea. Jewish law says one must go to a body of water which is outside the town. Many commentators say that in the time of the Black Death the custom became to do it at a private well or outside the city, not at a public well or inside the city, to reduce the chance of the Christians accusing the Jews of poisoning the well or, later, cursing the waters through magic incantations.
Once the Jews were accused of poisoning the wells, a wave of pogroms ensued. In January 1349, the entire Jewish community in the city of Basel was burned at the stake. The Jewish communities of Freiburg, Augsburg, Nurnberg, Munich, Konigsberg, Regensburg, and other centers, all were either exiled or burned. In Worms, in March 1349, the entire Jewish community committed suicide. In Cologne, the Jews were forced to flee.
In Mainz, which had the largest Jewish community in Europe, the Jews defended themselves against the mob and killed over 200 Christians. Then the Christians came to take revenge. On one day alone, on August 24, 1349, they killed 6,000 Jews in Mainz.
Of the 3,000 Jews in Erfurt, none survived the attack of the Christian mobs. By 1350, those Jews that survived the Black Death itself were destroyed by the ravages of the mobs. The Jewish communities in Antwerp and Brussels were entirely exterminated in 1350. There were almost no Jews left in Germany or the Low Countries by 1351.