NSW Health authorities say they have pinpointed the origins of the coronavirus infection picked up by a Sydney hotel quarantine worker.

The woman’s infection prompted warnings for thousands of Sydney residents to isolate if they had used some of the city’s busiest public transport routes, amid fears of a potential new community outbreak.

But on Friday, NSW Health Minister Brad Hazzard said genomic testing had determined the strain of coronavirus that had infected the woman was new Australia. It is thought to have come from overseas.

“It is highly likely it came from possibly the hotel or possibly aircrew that, of course, can stay overnight, stay for a few days, before they turn around and go back overseas,” he said.

“We will do some more work and report back to the community, but is extremely good news for all of us in Health and the NSW community.”

• For the latest NSW alerts and COVID information, visit here

The infected woman worked shifts at Novotel and the Ibis at Darling Harbour, although she had no contact with guests. One of those hotels is used as a medi-hotel.

“We still have work to do to determine which aircrew or person from overseas, possibly in the hotel, managed to transmit it … but [it is] definitely not a locally transmitted virus,” Mr Hazzard said.

NSW Health started testing all of the hotels’ staff after the worker’s infection was confirmed on Thursday. It also issued travel warnings for trains and light rail across Sydney.

The woman had taken trains and light rail from her home in Minto, in Sydney’s south-west, to work at Darling Harbour while she was thought to be infectious.

Anyone who travelled on the same routes was told to get tested and isolate until they hear from health authorities.

On Friday, Mr Hazzard said the travel advisories were being reviewed in light of the latest information.

“It is very likely that we will be able to lift that advisory later today,” he said.

Earlier, it appeared the re-emergence of the virus in the Sydney community might jeopardise the promised opening of the Western Australian border to NSW residents.

WA Premier Mark McGowan said on Thursday was too early to make a call on the December 8 opening. But he was worried a cluster could form from the new case.

“Obviously if the chief health officer recommends that we delay opening to NSW, then that is the decision we will make,” he said.

Tweet from @NSWHealth

Such an outbreak would also likely mean Victorians would also be barred from heading west without quarantine. WA is treating both states as one for the December 8 decision.

However, Queensland remains “very happy” with NSW’s progress on tracking down the origins of the worker’s infection.

Premier Annastacia Palaszczuk said no NSW resident should be too concerned about getting into Queensland for Christmas.

“Our chief health officers are speaking regularly and they’re very happy with the contact tracing that is happening at the moment,” Ms Palaszczuk told Nine’s Today show on Friday.

“We are watching it carefully to see if it turns into a cluster outbreak. But at the moment there’s no need for any concern from anyone, so continue with your plans.

“We’re monitoring it closely and if anything changes we will let people know.”

Queensland reopened its border to travellers from greater Sydney only this week.

On Thursday, NSW Premier Gladys Berejiklian said breaches of hotel quarantine were bound to happen, noting the state was due to welcome back its 100,000th returned traveller within days.

“This is a real test for NSW but I’m confident if we continue the path we’re on, that we will pass this test yet again.”

Victoria’s virus milestone

Victoria’s streak of days free of new coronavirus cases has hit 35, ahead of a weekend announcement about eased restrictions.

Friday’s figures, with 8784 tests in the previous 24 hours, mean Victorians have notched up five weeks without any new virus infections.

The milestone come with Premier Daniel Andrews expected on Sunday to confirm more easing of virus measures ahead of Christmas.

There will be another milestone on Monday, with five international flights due to land at Melbourne airport as Victoria’s revamped hotel quarantine program restarts for overseas travellers.

South Australia also confirmed no new cases in its Parafield outbreak on Friday. It remains at 33 infections.

SA has moved to immediately wind back some COVID rules.

-with AAP