State authorities have extended the deadline to October 31 for horse owners wanting to move their animals into the zone.
However, in shades of the Eagles song, Hotel California, you can check out any time you like, but you can never leave - at least not until state authorities give the all-clear.
Primary Industires deputy chief veterinary officer Ian Roth said horses can only be moved into the purple zone with a permit.
"Owners do need to be aware that once inside a purple zone their horses must stay there for an indefinite period.
"The previous deadline for movement into the purple zone was 19 October, but this date has been extended following recent changes in the boundary of the purple zone," Mr Roth said.
The purple zone was set up, and later enlarged, to allow thoroughbred breeding operations to recommence follow the equine flu outbreak.
However, it is an area of high exposure to the disease and animals must remain there until the all-clear is given. There are a number of colour-coded zones across New South Wales. While permits may be obtained to move horses from low-risk to high-risk areas, horse traffic is forbidden the other way.
Purple zone restrictions include mandatory disinfection of horse vehicles and equipment before leaving the zone.
The zone covers the greater parts of Penrith, Liverpool, Camden, Wollondilly, The Hawkesbury, Gosford, Wyong, Newcastle, Lake Macquarie, Port Stephens Great Lakes, Cessnock, Maitland, Dungog, Singleton, Upper Hunter, Muswellbrook, Tamworth, and the Liverpool Plains.
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