A quarantine is a restriction on the movement of people and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been exposed to a communicable disease, but do not have a confirmed medical diagnosis. The term is often used synonymously with medical isolation, in which those confirmed to be infected with a communicable disease are isolated from the healthy population. Quarantine may be used interchangeably with cordon sanitaire, and although the terms are related, cordon sanitaire refers to the restriction of movement of people into or out of a defined geographic area, such as a community, in order to prevent an infection from spreading. The word quarantine comes from a seventeenth-century Venetian variant of the Italian quaranta giorni, meaning forty days, the period that all ships were required to be isolated before passengers and crew could go ashore during the Black Death plague epidemic. Quarantine can be applied to humans, but also to animals of various kinds, and both as part of border control as well as within a country.