WA Premier Mark McGowan has announced that the State's borders will close to Queensland as the country reacts to the news that a Brisbane quarantine hotel worker has tested positive to the highly contagious UK strain of COVID-19.
The developments will mean as of midnight on Friday, travel from Queensland will no longer be permitted except for exempt travellers.
People who have arrived from Queensland since January 2 must go into self-quarantine until they have completed 14 days in WA.
Recent arrivals will also be required to be tested for COVID-19 by Tuesday, 12 January.
It's the right move, it's the smart pre-emptive move that's necessary in the world we live in.WA Premier Mark McGowan
Mr McGowan said the new strain set a "whole new benchmark" in the fight against the virus.
"The rulebook continues to evolve, as does COVID. As result, we cannot hesitate - we cannot sit back, wait and watch. With COVID-19 and this new strain we cannot assume anything," he said.
"Evidence shows this variant is 70 per cent more infectious than other strains - and we all know how easy the original strain of COVID-19 transmits through our community.
"Given the number of contacts and potentially affected venues and locations, we need to move fast. Queensland and the whole of Australia are on high alert."
The news came as Queensland Premier Annastacia Palaszczuk moved to put the greater Brisbane area into a 3 day lockdown as contact tracers work to establish the movements of the infected worker from January 2.
"I completely support Annastacia Palaszczuk's decision to put greater Brisbane into a 3-day lockdown - it's the right move, it's the smart pre-emptive move that's necessary in the world we live in," Mr McGowan said.
"Our thoughts are with our friends and family in Queensland. Tonight, when they go into lockdown, they are not just doing it for Queensland - they are doing it for the whole nation."
WA Police confirmed around 7,500 people have arrived in WA from Queensland since January 2, and a further 1,400 people were expected to land on 9 Brisbane-originating flights on Friday.
Testing clinics and frontline workers faced a tough day with temperatures expected to peak 41 degrees.
"From a health perspective, we are NOT telling people to rush to a COVID clinic today," the Premier said.
"The Department of Health will increase resources at our COVID clinics to ensure we can get through as many tests, as quickly as possible by Tuesday.
"But you do need to expect delays - just like we see everywhere around Australia and the world - so we ask everyone to be patient and to bring water and sun protection, in case the wait is long."
Mr McGowan said it may be wiser for people travelling from Queensland to simply turn around and head home.
"If you are a recent arrival from Queensland or arriving today, before midnight, you are free to depart WA and return to Queensland.
"You just need to follow the instructions from WA Police and our health professionals and provide the necessary information before you leave self-quarantine and prior to your travel."