Rabbit numbers are increasing on Wardang Island, where the deadly calicivirus disease was first put to the test.

Scientists at the Animal and Plant Control Commission confirmed on Monday that rabbit numbers had built up again on the small island off western Yorke Peninsula.

Calicivirus was released accidentally from Wardang Island - where it was being developed in an enclosed experimental site - in October 1995 before being officially released a year later.

The disease, which affects only European rabbits and was first reported in China in 1984, has reduced the numbers of rabbits up to 95% in some areas of Australia.

Drought conditions and immunity in some animals are blamed for the failure of the virus to take hold.

Individual animals which came in contact with the disease have developed antibodies making them immune to the virus.

But the scientists say genetic resistance passed on to the next generation of rabbits, which would make the whole species immune has still not been detected in Australia.

APCC senior researcher Dr Ron Sinclair predicted widespread outbreaks of calicivirus could be close at hand.

He said outbreaks usually follow breeding seasons, which in some areas have been delayed this year.

While samples showed there were two calicivirus outbreaks last year, there was yet to be one this season.

And tests indicated individual rabbits were immune to the disease, he said.

Two out of three monitoring sites, including the Flinders Ranges where the virus had been most successful in wiping out rabbits, have failed to record the virus in recent months.

"But right now because breeding has started in the south part of the State we're starting to get lots of young rabbits around" Dr Sinclair said.

"And they're all going to start to be susceptible."

However, Dr Sinclair said that controls such as calicivirus and myxomatosis would never get rid of every rabbit. Farmers had to rip up all the warrens on their properties to maximise the impact of the disease.

"People keep thinking calicivirus and myxo is the answer and will save them the trouble of ripping warrens and doing other things to control rabbits," Dr Sinclair said.

"If you just think a biological control control agent is going to get rid of your rabbit problem, you're fooling yourself."

The CSIRO was working on ways to spread a protein to rabbits to make them sterile.

Dr Sinclair said three years of research had been done and it would be another 10 years before the technology could be developed properly.