Victorian Premier Dan Andrews confirmed the worker had contracted the more infectious UK strain of the virus, the third such case to affect Australia's state-run hotel quarantine programs since the start of the year.

Video footage showed the guard obeyed all protocols, Mr Andrews said.

Mr Andrews told reporters he was happy to speak to the Prime Minister about whether "bespoke" quarantine facilities could be built away from major cities, but it appears the idea is dead in the water.

"That might give you some greater capacity and might be useful, not just for this pandemic but events that could occur in the future," Mr Andrews said.

"On the issue of risk, though, any facility will have to be staffed. Staff have lives. They have a family. You can put it 50 kilometres from where we are standing now or 500 kilometres, but there will be people there, too, and the virus spreads."

But Prime Minister Scott Morrison was quick to dismiss the idea.

"It remains the case that the most effective way to deliver at the scale that Australia needs to deliver these arrangements, that hotel quarantine remains the most effective way to do that. And that remains the advice I have from my experts and the alternative is not that clear to me," Mr Morrison said.

Purpose-built facilities or re-developing detention facilities to be used for quarantine was "persuasive" the Prime Minister said.

The government wouldn't be moving ahead with using a facility in Gladstone, an idea put forward by the Queensland government, but was still exploring a similar proposal in Toowoomba.

"This idea that you can replace the hotel quarantine system, bring Australians back home, manage your health agenda effectively through some other mechanism, I think we have to keep a sense of realism about this and a sense of proportion," Mr Morrison said.

READ MORE:

Both Mr Morrison and Health Minister Greg Hunt emphasised that more than 210,000 people had come through the hotel quarantine system in Australia, with only a handful of cases where the virus had spread out into the community.

Health secretary Brendan Murphy said the hotel quarantine system was more advanced now than it had been when it started, and was continually evolving to deal with the risks of the more transmissible strains.

"The most particular advances have been daily testing of all the quarantine workers, so you can pick someone who might pick up the virus very quickly, insisting on PPE, good-quality CCTV, moving some people in some states when they are positive to a hotel that doesn't mix them with negative people," he said.