Queensland's chief veterinary officer, Dr Ron Glanville, said Hendra virus was quite different from equine influenza and should not be confused with EI.
"There is no relationship between the two," he said. "I want to reassure Queensland horse owners and horse industries that we are not facing a lockdown situation or movement restrictions.
The Hendra virus is believed to be carried by flying foxes, or fruit bats.
Biosecurity officials continued with tests on samples from 37 horses at the Brisbane vet practice today while working with Queensland Health and horse industry groups to ensure that the risks involved the virus are widely known.
Dr Glanville said officials were alerted by a private veterinarian about the sick horses on Monday.
The symptoms were not consistent with signs previously seen in Hendra virus cases and the decision to quarantine the property was initially a precautionary measure because of the severity of the illness in the affected horses, rather than suspicion of Hendra virus.
However, as part of its routine procedures, Biosecurity Queensland tested for a range of diseases including Hendra virus, which was confirmed as the cause yesterday.
Hendra, first isolated in 1994 in a Brisbane outbreak which killed 14 horses and trainer Vic Rail, can be transferred from horses to humans, but it is extremely rare.
This is the ninth case of Hendra virus in Queensland since 1994. Of the three people known to have contracted the disease, two died.