Queensland recorded its first case of the virus in five years when the positive test came back in Mackay on July 8.

The Mackay Public Health Unit identified five people who were in contact with the horse while it was infectious and two of those will receive monoclonal antibodies.

One is deemed high-risk and the other is moderate-to-high-risk, Mackay Hospital and Health Service told AAP in a statement.

No one exposed to the horse in Mackay has been hospitalised.

One horse on the property where the positive case was identified has already been euthanised, Biosecurity Queensland said.

Chief Veterinary Officer Dr Allison Crook said the horse had not been vaccinated against the virus.

"Hendra virus infection can occur throughout the year, so it's important that horse owners take steps to protect themselves and their animals at all times," she said.

"If a horse becomes sick, owners should contact their veterinarian immediately."

The virus was discovered in 1994 following an outbreak of illness amongst horses at a racing stable in the Brisbane suburb of Hendra.

It can spread from flying foxes to horses, horses to horses and in rare cases, from horses to people. It can be fatal in humans.

Australian Associated Press