In other news, just one property remains to be formally cleared, although there have been no fresh known infections in the state since about December 9.
There is also one property still officially listed as suspect.
Latest figures from the Department of Primary Industries show 6626 properties have been resolved.
The news comes as new requirements come into force for horse movements within the once highly infected purple zone.
Horse owners must now carry documentation of immunity and a Travelling Horse Statement for any horse movements in the purple zone.
Owners were reminded that proof-of-immunity is a temporary requirement. This may be lifted if the purple zone is progressed to Green, as expected, in mid-March.
This temporary requirement has effectively halted the arrival of New Zealand horses at Sydney Airport, as any horse from New Zealand would need to have been fully inoculated with the vaccine being used in Australia. That vaccine is not approved for use in New Zealand, making the requirement impossible to meet.
Authorities in Australia point out that by delaying a horse move by a "matter of weeks", if an owner has this option, could save people the cost of obtaining such proof.
The documentation best used to demonstrate a horse's proof of immunity is the Certificate of Immunity: this certificate is completed by your vet.
It certifies that a horse is considered "immune" to equine influenza (EI) on the basis of having recovered from infection (a recovered horse) or being appropriately vaccinated with the ProteqFlu vaccine.
A property's "resolved" status does not give individual horses proof of immunity.
The purple zone extends from south of Sydney through to the Central Coast, Newcastle, Maitland, Scone and Tamworth.
Primary Industries Minister Ian Macdonald said the short-term requirement in the purple zone was an essential step if the zone is to be declared flu-free in March.
"We are on target for the March goal, with only one property in NSW still having infected horses and about 80 per cent of proof-of-freedom testing successfully completed.
"Only when testing confirms there are no isolated pockets of infection remaining will we be in a position to revoke the purple zone and lift movement restrictions.
"This should be very soon if testing continues to confirm that EI has burnt out.
NSW chief veterinary officer, Bruce Christie, said the deadline for first-round vaccinations expired yesterday.
The vaccination programme is now winding down, with only second-round vaccinations due to be completed.
"If you have horses in the purple zone that have not been infected or vaccinated, they cannot be moved until the current restrictions have been lifted.
"It remains vital that all horse events in the purple zone are registered with the NSW Department of Primary Industries until we can prove that EI has burnt out.
"For horses to leave the purple zone a permit is required."