Scott Morrison has issued a warning to holiday-makers in Queensland to “stay where you are” during the three-day lockdown in Brisbane, as states rush to introduce 14-day self-quarantine rules for returning travellers.

Western Australia, South Australia, the Northern Territory, Tasmania and the ACT have now all issued new self-quarantine rules for people who have been in Brisbane since January 2, requiring them to self-quarantine on return for 14 days.

The border between NSW and Queensland remains open but people are expected to abide by the three-day stay at home order if they are in Brisbane or have returned since January 2.

The dramatic measures follow confirmation a hotel quarantine cleaner is believed to have been in the community for five days while unwittingly infectious with the “mutant” UK COVID-19 strain that is ripping through London.

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The Prime Minister has also warned he “can’t guarantee” that more states will not be plunged into snap lockdowns if it emerges that the “mutant” virus strain has escaped interstate.

“We’ll see,” Mr Morrison said on Friday.

“That’s my honest answer. I can’t tell you what we don’t know. No-one can.

“We don’t want to learn the hard way on this. That’s why I think the decision of the Queensland Premier today, in this case, has been very wise and prudent.”

He issued a strong warning to holiday-makers in Queensland to remain in Brisbane if they are in the areas declared a hotspot.

“Our message to Australians who are in those areas is – stay where you are,” he said.

“Don’t go anywhere. Don’t go home to another state or any other part of your state. Over the next few days, stay where you are. If you’re somewhere else and you are planning to go there, don’t.”

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For Queenslanders already in other parts of the country who have been in Brisbane since January 2, he urged them to “get tested”.

“If you are from any of those places and you are somewhere else, you may be here in the ACT, you may be in Western Australia, you may be in Victoria – you should treat yourself as if you are in those places,” he said.

“You should get tested. You should monitor your symptoms.

“The situation in Brisbane is a serious situation. Yes, we know there is only one case,” the Prime Minister said.

“But what we do know is that this new strain is some 70% more transmissible than the previous strains of the virus.”

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WA Premier Mark McGowan took the swiftest and strongest action, announcing he was once again slamming the state border shut.

Exempt travellers will be tested upon arrival, must self-quarantine for 14 days and tested for COVID.

“This is a dangerous situation, not only for Queensland but for the whole of Australia,” Mr McGowan said.

“We cannot hesitate. We cannot sit back and wait and watch.

“We need to move fast.”

WA has now locked out travellers from NSW and Victoria, and now Queensland.

The Prime Minister said the idea that you could simply suspend travel from Britain and keep the virus out of Australia was a “false hope”.

However, in the short-term Australia will reduce the caps on international arrivals into Sydney, Brisbane and Perth.

“We will be reducing – till the 15th of February – the caps on international arrivals in New South Wales, Western Australia, in Queensland.

“That means, in New South Wales, there’ll be a weekly cap of 1,505,” he said.