Queensland is closing its borders to roughly one million Sydney residents after the city's Bondi Covid cluster grew to 21 cases on Tuesday.
From 1am on Thursday, the state will close to the city of Sydney, Woollahra, Bayside, Canada Bay, the Inner West and Randwick, Queensland Premier Annastacia Palaszczuk said on Wednesday.
The state has already been closed off to those living in the Waverley Council area.
Queensland has followed Victoria in banning residents from the seven Sydney council areas.
Anyone who has been in those areas and will arrive home after the cut-off time will need to quarantine for 14 days.
"We cannot afford to have this Delta variant out in our community," Ms Palaszczuk said.
"We want everyone to be safe and we wish NSW the very best in getting on top of this particular event."
The closure comes just one week before school holidays, a factor which was not taken lightly, Deputy Premier of Queensland Steven Miles said during the presser.
WA and SA shut borders to all of NSW
Western Australia and South Australia reinstated hard borders with all NSW on Wednesday afternoon, effective immediately.
South Australia's border closure excludes a 100-kilometre buffer zone for cross border communities along the SA-NSW border.
Western Australia shut its border to NSW after reclassifying the state as "medium risk".
"Travel from or through NSW is no longer permitted, except for exempt traveller," Western Australia Premier Mark McGowan said on Wednesday.
Exemptions may also be granted on compassionate grounds including for West Australians who need to return home.
Those travellers must self-quarantine for 14 days upon arrival and present for two coronavirus tests during that period.
Speed of variant's spread influenced Queensland decision
Queensland Chief Health Officer Dr Jeannette Young said the detail that prompted the decision to shut its border to a million Sydneysiders is how fast the Delta variant seen in Sydney can spread.
"With the Delta variant, we're seeing very fleeting contact leading to transmission. If you remember at the start of this pandemic, I spoke about 15 minutes of close contact being a concern," she said."
"Now, it looks like it's 5-10 seconds that's a concern. So it's just the risk is so much higher now than it was only a year ago."
Covid spreads in Brisbane hotel quarantine
Queensland recorded one new case in hotel quarantine on Wednesday. It is believed the person contracted it from someone else in hotel quarantine who has already tested positive.
Previously reported cases involve a couple who have been in quarantine at the Brisbane Airport Novotel Hotel since June 8. They became infected when another traveller with Covid was placed in the room next door on June 10, Chief Health Officer Dr Jeannette Young said.
"So we're contacting all of the 30 people in that floor 5 and anyone who left quarantine during the period I'm concerned about," she said.
"The people on floor 5, their stay has been extended until we've been able to confirm that there's no additional transmission."
Victoria bans seven Sydney 'red zones'
Late on Tuesday, Victoria's Chief Health Officer Brett Sutton declared seven Sydney local government areas "red zones" under Victoria's travel permit system.
The move effectively banned residents from the municipalities of the City of Sydney, Waverley, Woollahra, Bayside, Canada Bay, Inner West and Randwick from entering Victoria from Wednesday.
"If you enter at an airport or seaport from a red zone without a permit, you will be fined and will stay in hotel quarantine until return transport is arranged," the Health Department said.
Victorian residents who have been in a red zone - other than for transit - can still return to the state with a permit but must self-isolate at home for 14 days.
Wollongong has been listed as an orange zone, meaning incoming travellers to Victoria must get tested soon after arrival and isolate until they receive a negative result.
Non-essential travel into Victoria from red or orange zones is being strongly discouraged.
However, Victorians are being welcomed back to other states in time for the southern state's school holiday period.
South Australia and Queensland will reopen their borders to Victoria from Friday.
Infected passenger flies to New Zealand
Earlier on Wednesday, NSW Health issued a health alert after a person infected with the virus flew from Sydney to New Zealand and back.
The alert was for passengers travelling on Qantas flight QF163 on Friday night to Wellington, and anyone who flew on Monday morning on Air New Zealand flight NZ247 from Wellington to Sydney.
Passengers on board those flights must contact NSW Health immediately, get tested and isolate for 14 days regardless of the result.
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