A new coronavirus case diagnosed in Queensland is connected to another announced two weeks ago, with the missing link between the pair likely still in the community.
Genomic testing on Friday confirmed the 26-year-old's case was linked to a hospital worker whose infection was announced on March 12.
Queensland Chief Health Officer Dr Jeannette Young said it is likely that an unidentified intermediary had passed the virus onto the Stafford man.
He tested positive on Thursday and visited at least nine different venues across the city after he became highly infectious last Friday.
The venues the man visited between Saturday and Thursday include Carindale Westfield, Gasworks at Newstead and Bunnings, Aldi and Guzman y Gomez at Stafford.
"We will know more in the next 24 hours, but in the meantime, those identified as visiting the locations in today's Public Health Alert should immediately get tested and isolate until you receive your results," she said in a statement on Friday night.
Health authorities are tracking down close contacts of the man, who will have to undergo quarantine.
Anyone who visited Mamma's Italian Restaurant at Redcliffe on March 21 between 12.40pm to 3.10pm will now be required to isolate for 14 days.
The infection sent Brisbane's hospitals into lockdown for the second time in a fortnight.
Aged care facilities, prisons and disability services are also shutting their doors for the next three days to stop the virus spreading to vulnerable people
Everyone in the Brisbane City and Moreton Bay council areas are being urged to wear masks in crowded places and socially distance.
"It is absolutely imperative over the next few days if you are sick and unwell to stay home and go get tested, it is absolutely critical we do this over the next two to three days," Ms Palaszczuk told reporters.
NSW and Tasmanian health authorities advised recent arrivals who had been to any of the venues identified to self-isolate and contact public health authorities in their state.
In health alerts issued late on Friday, NSW and Tasmania also advised people who had been to the venues visited by the Stafford man not to travel to the states.
NSW Health said from Saturday anyone who has been in the Brisbane City Council or Moreton Bay Regional Council areas will have to fill out a passenger declaration form confirming whether they had visited any of the venues of concern.
Dr Young said the man is being treated in Royal Brisbane and Women's Hospital.
His housemates in Stafford are all self-isolating and getting tested.
The man was working as a landscaper in Paddington on Monday when he started feeling ill.
"Anyone who's been to any of these venues during those specific timeframes, I want you to come forward and get tested, whether or not you've got symptoms, and to remain in isolation until you get a negative result," Dr Young said.
The man visited Aldi at Stafford on the day he was tested for COVID-19 but before he had got his result.
Dr Young brushed off concerns he hadn't followed health advice, saying he had only "popped in" to the store briefly.
The coronavirus-infected doctor who the man's case is linked to worked a shift at the Princess Alexandra Hospital and visited four venues in the city's south while she was infectious.
In response to that infection the government locked down hospitals, aged care facilities, prisons and disability providers for seven days to avoid a wider outbreak.
That lockdown only ended last Friday, with those facilities now barring public visitors again.
Queensland reported another six virus cases in hotel quarantine on Friday, taking the number of active cases to 69.
The state has administered 53,893 vaccine doses.
Australian Associated Press