Western Australia’s premier is not ruling out delaying the reopening of interstate borders after a Sydney hotel quarantine worker tested positive to COVID-19.

WA is scheduled to open up to NSW and Victoria from December 8, with travellers from those states no longer required to quarantine for 14 days.

But those plans are under a cloud as WA health authorities seek further information from their NSW counterparts.

Urgent genomic testing is under way to determine how the woman contracted the virus, with results due within 48 hours.

Authorities are concerned the woman, who appears to have caught public transport while symptomatic, may have been infected through another worker.

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“This is why we were very cautious about reopening,” Premier Mark McGowan said on Thursday.

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

“We don’t have enough information at this point in time to make that decision but we expect to get more information over coming days.”

Queensland authorities said on Thursday that their borders – which opened to Sydney residents only on Tuesday – will remain open for now.

“The government is keeping a close eye on what is happening in Sydney and our health experts are in regular contact with their NSW counterparts,” Health Minister Yvette D’ath told the Queensland parliament.

NSW Premier Gladys Berejiklian said the hotel worker’s case was a “very serious situation” and a “stark reminder” that the virus remained a threat until a vaccine was widely available.

Ms Berejiklian also indicated that a promised easing of restrictions from Monday would still go ahead as planned.

“At this stage, the health advice doesn’t require us to [go backwards],” she said.

“But if the next few days, the situation changes and health advice changes I will not hesitate to act as the Premier.”

Gladys Berejiklian said a swathe of virus restrictions will still be eased. Photo: Getty

Health Minister Brad Hazzard echoed said he was not “overly fussed” about the new case.

Depending on the scale of the outbreak in NSW, WA could also delay reopening its border to Victoria.

The two states are being effectively considered as one jurisdiction by WA health authorities, given the flow of travellers.

Mr McGowan said he expected to make a decision over the weekend.

“I realise this is very disruptive to many people and very problematic to many people because they don’t know what’s happening,” he said.

“But at the same time, we have to make decisions that are based upon health advice and based upon the safety of the state.

“The NSW government is confident they have it under control but we want to see and make sure that the evidence supports that before we make a final decision.”

The Premier said he had contacted Ms Gladys Berejiklian and offered contact tracing support.

The woman’s diagnosis has prompted health authorities to ask scores of people who might have been in contact to “stop and stay”.

Anyone who worked with the woman or caught the same train between Minto and Darling Harbour is being asked to get tested and isolate until they hear from health authorities.

“It’s sort of a hold and stay until we’ve assessed the extent of what is going on,” chief health officer Kerry Chant said on Thursday.

Urgent genomic testing is under way to determine how the woman contracted the virus, with results due within 48 hours.

Authorities are concerned the woman may have been infected through another worker.

“She didn’t have contact with infected overseas quarantine patients directly … so at the moment, there isn’t a smoking gun in terms of how we would say the transmission event happened,” she said.

Travellers from NSW and Victoria have been blocked from entering WA for almost nine months unless they went into quarantine and, until recently, secured exemptions.

Travel from South Australia in WA remains prohibited unless arrivals meet strict exemption criteria and isolate for 14 days.

WA has had no community transmission of the virus since April.

-with agencies