The WA Chief Health Officer is seeking urgent advice from New South Wales after a Sydney quarantine hotel worker was diagnosed with COVID-19.
Premier Mark McGowan has previously said any outbreak in NSW or Victoria would prompt WA to close the border.
NSW Health Minister Brad Hazzard says he was notified of the new case early on Thursday.
“She worked at the Novotel and the Ibis at Darling Harbour. One of those is a police quarantine hotel,” he told Seven’s Sunrise program.
“The good news is her five family members were tested overnight and they are all negative, so that is a good outcome.”
WA had planned to open the border with NSW and Victoria on December 8.
WA Chief Health Officer Andy Robertson is seeking advice on the matter from his NSW counterpart before any further decisions are made.
NSW Health is asking anybody who worked at the Ibis last Friday or at the Novotel on Saturday, Sunday or Monday to monitor for symptoms, self-isolate and get tested.
The news comes a day after NSW recorded 25 straight days without a single COVID-19 case in the community and Premier Gladys Berejiklian announced a swathe of social restrictions would be eased from Monday.
Chief Health Officer Kerry Chant said on Wednesday she believed the state had “probably virtually eliminated” community transmission.
Ms Berejiklian said she anticipated there would be more cases.
Mr Hazzard said he also anticipated there would be more cases “because we are in a pandemic”.
“What we have done is open up NSW in a way that is probably world-leading at the present time. I think we have led the way in Australia,” he said.
He also urged anyone with any symptoms to get tested as soon as possible.
“Please don’t go to work, please don’t go shopping and stay home,” he said.
Meanwhile, NSW Health is calling on people in Sydney’s northwest to get tested if they have even mild COVID-19 symptoms after traces of the virus were detected at a sewage treatment plant in Riverstone.
Fragments of the virus were detected in samples taken on Sunday from the sewerage system that drains parts of Riverstone, Vineyard, Marsden Park, Shanes Park, Quakers Hill, Oakville, Box Hill, The Ponds, Rouse Hill, Nelson, Schofields and Colebee.
Detection of the virus in sewage samples could reflect the presence of known cases of COVID-19 diagnosed in recent weeks in the area.
However, NSW Health is concerned there could be other active cases in the local community in people who have not been tested and who might incorrectly assume their symptoms are just a cold.