KHV is known to have a lifetime of approximately 24 hours without a fish host. Like others said above, some of the fish parasites can live for a significant period of time without a host, at least a day, for some several days, for a few a week may be possible.
Certainly a week hold time will dramatically reduce the possibility of a virus or parasite contamination.
Be aware however that birds, frogs, and a variety of other wildlife can bring parasites to the pond. The normal sources are new fish, new pond plants, and fresh lake water.
Your koiphen chemist and environmental scientist.