The alarming number of cases have seen affected properties in both New South Wales and Queensland under lockdown, and horses exposed to the animals that fell ill being closely monitored.
The latest case is on a property near Macksville on the Mid North Coast - the second in New South Wales in the current spate of cases.
"The property has been placed in quarantine and the dead horse has been buried," the state's chief veterinary officer Ian Roth, said.
"There are three other horses on the quarantined property which are currently showing no signs of illness," he added.
The state's health director of the Centre of Health Protection, Dr Jeremy McAnulty, said six people who have had close contact with the infected horse will be closely monitored for any symptoms of the infection.
"Public Health Unit staff have interviewed these people to assess their level of exposure," he said.
The earlier property in NSW to be hit by the virus was at Wollongbar, and was placed under quarantine last Thursday.
In all, four companion horses and 15 people who have been in contact with the affected horses are being monitored in the state.
"The single surviving companion horse on the Wollongbar property remains in good health and initial tests for Hendra have returned negative, which is a good sign," Roth said.
Mr Roth said a veterinarian took samples from the horse near Macksville after it had died last Sunday.
"Samples from the dead horse were sent to department's Elizabeth Macarthur Agricultural Institute for laboratory analysis and results confirmed the Hendra virus.
"Horse movements on and off the property are being checked by veterinary staff."
He said there were no current horse-movement or people-movement links to the Wollongbar property or the recent Hendra outbreaks in Queensland.
"The horse had been in a paddock containing a fig tree, so it is likely that flying foxes were the source of infection," he said.
The virus is known to be carried by flying foxes - a native fruit bat - and can be passed to horses.
McAnulty said all human infections that have occurred have been linked to high-level exposures to infected horses.
"There has been no evidence of human-to-human or flying fox-to-human spread of Hendra virus.
"Horses may shed Hendra virus before they show any signs of illness so it is always important to use good hygiene practices when around horses," McAnulty said.
People are advised to cover any cuts or abrasions on exposed skin before handling horses and wash their hands well with soap and water, especially after handling a horse's mouth or nose - for example, fitting or removing a bridle - and before eating, smoking or touching your eyes, nose or mouth.
Don't kiss horses on the muzzle - especially not if the horse is sick.
Use personal protective equipment to protect yourself from the body fluids of horses.
Authorities are advising horse owners to take precautions in areas with flying foxes to reduce the risk of their horses becoming infected: