The West Australian Health Minister says a patient at Perth's Fiona Stanley Hospital (FSH) appears to have contracted hepatitis C in theatre last year.

But Health Minister Kim Hames said it was not known how it happened.

"It was avoidable, something went wrong, and even now we can't pinpoint exactly what it was," he said.

An investigation was carried out after the former patient was found to have had hepatitis C some months after being at the hospital for a procedure.

The discovery was made after the person, whose identity and sex cannot be revealed for reasons of confidentiality, had a blood test in September.

The patient had been in theatre at FSH for an unrelated issue in February; their procedure had immediately followed that of a patient who did have the virus.

Patient followed a complex case in theatre

The operation was after hours, in what has been described as an "urgent" situation.

Director General of the Department of Health, Dr David Russell-Weisz, said the first patient, or case one, was "extraordinarily complex and very difficult".

"That case one was very difficult to cannulate, to put a tube into a vein in the arm, it was very, very rare," he said.

"What I can say, is the investigation was thorough.

"We investigated all parties involved, from the people in theatre, to the people right through the hospital that might have had contact with this patient, we left no stone unturned."

The transmission occurred at a time when problems with sterilisation of instruments had arisen.

But Dr Russell-Weisz said that had been ruled out as a factor.

"What the investigation has showed is that it was more likely that this happened in the theatre, it's very very rare, but it was not sterilisation."

Health Minister says hep C is a curable disease

Dr Hames criticised suggestions that hepatitis C was an incurable virus.

"Twenty percent, roughly, of patients spontaneously have remission, like you might with any virus," he said.

"There's medication that currently cures 70 per cent and a new one coming on the market in three weeks, authorised by the Federal Government, gives 100 per cent cure.

"So it is a curable disease, but certainly not satisfactory that this should occur."

The patient fully recovered and it is understood they did not show any hepatitis C symptoms, or know of any by the time the blood test occurred in September.

While there have been cases in other states, it is believed to have been the first time hepatitis C has been transmitted in a WA hospital.

Independent physician called in to investigate

Infection control officer for Sir Charles Gairdner Hospital Dr David Speers was called in to give an independent perspective as part of the inquiry.

An expert on hepatitis, Dr Speers said all aspects of the patient's experience were looked into.

"There have been some incidents of transmission through anaesthetic tubing which you could say is airborne, but we investigated that possibility and there was no sharing of anaesthetic tubing in this case," he said.

"Hepatitis C transmission is almost always about blood to blood transmission but the amount of blood that can lead to transmission of hepatitis C can be microscopic and invisible, the amount can be extremely small."

Dr Speers said the committee effectively came to the conclusion that the second patient was unlucky.

"This was a series of unusual and extremely rare events which led to this incident potentially happening because we couldn't definitively prove the route of transmission," he said.

Recommendations were made for improving tracking and recording of procedures.

Concerns over leaked stories and breach of trust

The Australian Medical Association (AMA) said it was satisfied that the issue has been thoroughly and properly investigated.

But AMA WA president Michael Gannon said he still had concerns.

"There is no circumstance where someone should be exposed to a very serious infectious agent like hepatitis C," he said.

"This goes to the quality of care being provided in Fiona Stanley Hospital 12 months ago, and also goes to the toxic environment in which people are still leaking these kinds of stories.

"We've got this horrible breach of trust between the administrators in Fiona Stanley Hospital and the clinicians and that's why stories like this come out."

Dr Gannon said it was important for the new health minister to get off to a "flying start" to rebuild trust.

Opposition says Government forced to reveal details by publicity

Labor's health spokesman Roger Cook said the opposition was concerned issues surrounding privatisation may have contributed.

Mr Cook said the Government had only been drawn to reveal details of the case following publicity in the media.

"We're surprised the Government hasn't been more open and accountable up until now, and it's only because this issue is in the media that the Government is actually coming forward with answers," he said.

"This information has come out through unofficial channels and it's another sign of how unhappy senior clinicians are at this hospital."

Mr Cook said it was important to know that such issues were not occurring on a regular basis.

Health Minister says he is proud of FSH staff

Dr Hames suggested there was a silver lining to the seemingly endless run of "bad news" stories about FSH.

"Labor Party and the AMA can keep attacking Fiona Stanley as much as they like because what it does is it stimulates all those people that have a great result to get in touch with me, so I've never had more letters," he said.

"I've never had more people stop me in the street than now and say 'don't listen to what's being presented about Fiona Stanley, we went there and we had a great experience'."

Dr Hames said 100,000 people had been through the hospital in the past year and he was extremely proud of FSH staff.

Dr Gannon said he did agree there were good news stories out of Fiona Stanley Hospital "every day", and the overall quality of care was high, but said it was sad if doctors were shouted down when they tried to shine a light on problem areas.