WA Premier Mark McGowan on Tuesday confirmed three people in Perth hotel quarantine had now been found to have the more transmissible variant after NSW, Victoria and South Australia had all previously recorded cases in returned overseas travellers.

The UK variant is believed to be up to 70 per cent more infectious than the original, causing havoc in England and prompting British Prime Minister Boris Johnson to order a new national lockdown until at least mid-February.

Victorian Emergency Services Minister Lisa Neville said the state had seen up to five cases of the UK strain so far.

"(Our) job is to make sure that our hotel quarantine system is as robust and strong as possible, that this does not get out, whether it's the UK strain or any other strain," she said.

Ms Neville said health authorities are also becoming increasingly concerned about the number of positive COVID-19 cases among international flight crew who are quarantining in Melbourne.

Eight out of just over 1000 flight crew who have arrived in the last two weeks have been positive.

"This is over and above the averages we are seeing in international returned travellers," Ms Neville said.

Last month, the Victorian government started requiring all returning international flight crews to go into mandatory hotel quarantine.

"Everyone needs to follow the lead around quarantining and testing the fight crew, it is absolutely critical given the numbers we are seeing."

For NSW, Chief Health Officer Kerry Chant said there was "no one silver bullet" to keep the community safe from variant viruses which are moving across the world.

"Just because you're tested a couple of days before you get on the plane, you can develop the infection on the plane, you can develop as you're getting off the plane, or the next day," she said.

"It is about that universal approach, making sure we treat anyone with COVID as highly infectious and making sure we go through all of the end-to-end chains to ensure that we don't have any incursion events in our community."

Acting NSW Premier John Barilaro said measures would always be put in place to protect Australians.

"We're learning, like any other nation, there's no playbook or rule book that shows you how to manage a global pandemic at the scale we've seen," he said on Tuesday.

Dr Chant said she had been in contact with other countries to assess how variants are affecting immune-compromised patients.

"Clearly, there's concerns of this emergence of strains, not just from the UK but in other parts of the world, that may be associated with increased transmissibility," she said.

"Recognising the rate of disease internationally is increasing, so the threat level is never higher than at the current time."

Another international strain - a South African variant - was detected in a woman who arrived in Queensland on December 22 who went straight into hotel quarantine.

More than 30 countries around the world have recorded cases of the South African or UK coronavirus variants including the US, Lebanon, Singapore, Pakistan, India, South Korea, Japan, France, Germany and Italy.

The World Health Organisation is yet to determine whether the new variants could undermine COVID-19 vaccines being rolled out around the world.

Australian Associated Press