A horse died at the Cawarral property on August 8, sparking the alert. Testing confirmed it had died from the virus, which is carried by native fruit bats.
However, two other horses at the property had died in the preceding fortnight and the Department of Primary Industries set about establishing the causes of those deaths. One of those horses, that died on August 7, returned a positive test.
The third horse, which was the first to die, could not be tested beacuse its carcass had been destroyed.
All 25 horses that remain on the property have been tested for the virus, with one so far returning a positive result. It has been retested to ensure the result was not a false positive. The results are expected early this week.
The property, the J4S Equine Nursery, remains under quarantine, as does an adjoining property. Horses removed to eight other properties before the premises went into lockdown are also under movement restrictions.
All horses will continue to be tested for the virus, as it has an incubation period of 5 to 16 days.
All horses on the quarantined and trace properties will remain under movement restrictions until Biosecurity Queensland is confident there is no further infection.