Three horse stud workers under observation in hospital for the Hendra virus could be discharged as early as next week, the father of one of the patients says.Stud manager Debbie Brown and colleagues Adrian Daniels and Angela Webber are at significant risk of contracting the potentially fatal virus, after coming into close contact with infected horses at J4S equine nursery in Cawarral, northeast of Rockhampton.They have so far tested negative, but are waiting out the virus's incubation period und

Three horse stud workers under observation in hospital for the Hendra virus could be discharged as early as next week, the father of one of the patients says.

Stud manager Debbie Brown and colleagues Adrian Daniels and Angela Webber are at significant risk of contracting the potentially fatal virus, after coming into close contact with infected horses at J4S equine nursery in Cawarral, northeast of Rockhampton.

They have so far tested negative, but are waiting out the virus's incubation period under supervision at the Princess Alexandra Hospital in Brisbane.

The virus is estimated to take up to 14 days to incubate from the day of exposure.

The three patients are being monitored at the same hospital where Rockhampton vet Dr Alister Rodgers is fighting for his life after contracting the virus from one of the sick horses on the property.

Lloyd Webber, father of 24-year-old Ms Webber, told AAP his daughter's chronic headaches had stopped on Sunday.

He attributed the headaches to a trial drug used on the stud workers and the vet to prevent the viral infection.

"They have pulled through the treatment which they were sick from," Mr Webber said.

"I think they are all feeling pretty good at the moment.

"I think they have had the best treatment and Queensland Health could not have done more for them and all the criticism is unfounded and really unfair."

He said his daughter told him all three could be discharged as early as next week if a second round of tests were also proved negative.

"She should be right but we know it can appear suddenly as it did with the vet," Mr Lloyd said.

"They will do another test to make sure she's negative by the end of the week.

"They have at least another week in hospital."

He said it took the family some time to convince his daughter to stay in hospital as being away from her 22-month-old daughter Dakota has been difficult for her.

Her partner Shaun Griffiths drove 650km from Rockhampton to Brisbane to ensure Ms Webber remained under observation.

Two dead horses at the J4S horse stud in Cawarral tested positive to the virus in early August.

A third horse on the property tested positive on Saturday and will be euthanased.

A foal that died on July 28 is believed to also have had Hendra but the Department of Primary Industries says its carcass was destroyed before it could be tested.