The Redcliffe Vet Clinic has been quarantined after laboratory tests last night confirmed three horses from the practice were infected with the rare Hendra virus.

The disease was first identified in 1994 following the death of a Brisbane horse trainer and 16 of his horses, however authorities insist horse-to-human infection is rare.

One horse at the bayside clinic has died, another was euthanized yesterday and a third is recovering from the virus.

Biosecurity Queensland's epidemiologists are working with the practice to determine how and when the infection occurred.

"We are taking the situation seriously with biosecurity inspectors moving quickly to quarantine the practice and establish thorough disinfection procedures to ensure the area is fully contained," Queensland Minister for Primary Industries and Fisheries Tim Mulherin said.

"We don't yet know how the virus came to be at the vet practice, however epidemiologists are investigating and conducting complex investigations.

"We are also working with local neighbours to ensure they are aware of the situation and the quarantine."

Biosecurity Queensland chief veterinary officer, Ron Glanville, said the case was unusual, as the horse's symptoms had not been consistent with signs seen in previous Hendra cases.

"Hendra is a serious but rare virus which occasionally affects horses," Dr Glanville said.

"As a zoonotic disease, it can also spread from horses to humans, but that is also rare.

"Of those diagnosed with the virus, one horse has died, one is recovering, and one was euthanized early this evening."

Biosecurity Queensland will today sample 37 other horses which are located at the practice.

"However the first priority is containment and disinfection," Dr Glanville said.

The vet practice was quarantined on Monday night as a precautionary measure after some horses displayed unusual symptoms.

While it is extremely difficult to contract the disease, staff from Queensland Health are contac ting people involved with the sick horses to advise on personal health and hygiene issues associated with the disease.