The practice of quarantine being used today developed nearly 500 years ago in Venice as the city attempted to protect itself from the plague. As the Centers for Disease Control and Prevention describes it: "Ships arriving in Venice from infected ports were required to sit at anchor for 40 days before landing. This practice, called quarantine, was derived from the Italian words quaranta giorni, which mean 40 days." The latest quarantine, in Yumen city, Gansu province, was lifted after nine days.

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