The Queensland government is racing to avoid Brisbane's fourth lockdown this year after three locally acquired cases of COVID-19 were recorded in the the city.
Premier Annastacia Palaszczuk says the three cases include a 12-year-old boy who flew into the state from Sydney on July 9 and his father.
A fully vaccinated Brisbane Airport worker has also tested positive, which is a major concern for authorities.
Ms Palaszczuk says a face mask mandate due to end on Friday for 11 local government areas will be extended for another seven days.
"That is to avoid a lockdown, we just want to make sure we get on top of those cases and we want to make sure that we keep everybody safe," she said.
"So another week of wearing masks, but it is the right thing to do."
Brisbane has already been locked down three times this year amid COVID-19 outbreaks in January, March and in June-July.
In other rules that have been extended, home gatherings are limited to 30 people and venues have to ensure there's only one patron per four square metres.
There are limits on visitors to hospitals, aged care providers and residential disability providers.
The restrictions will be in place until July 23 in Brisbane City, Logan, Moreton Bay, Ipswich, Redlands, Sunshine Coast, Gold Coast, Noosa, Somerset, Lockyer Valley and Scenic Rim.
Chief Health Officer Jeannette Young said the boy had been in the US for three months before arriving with his mother at Sydney Airport on June 21.
They quarantined for 14 days in Sydney before flying to Brisbane on Qantas flight 544 on Friday.
The boy is believed to have passed the virus to his father at their home at Newport on Brisbane's Bayside. The mother has tested negative, but is in hospital with her son as a precaution.
Dr Young said it was uncertain whether the boy picked up the virus in hotel quarantine or elsewhere.
The father worked at a Sunshine Coast office on Wednesday, but Dr Young believes the family haven't visited many venues.
Queensland health updated a list of exposure sites on Thursday between Friday 9 July and Wednesday 14 July, including Qantas Flight QF544 Sydney to Brisbane, Brisbane Airport and the international terminal.
Also on the list were a number of Aspley businesses including Aspley Medical Centre between 2pm and 3:45pm on Tuesday and Pharmasave Pharmacy Aspley between 3:45pm to 4pm the same day.
Dr Young said the third case in a female airport worker was "very concerning".
The woman in her 40s is fully vaccinated with Pfizer and worked three night shifts on Monday, Tuesday and Wednesday while infectious.
"I don't know exactly where they work at the airport, we will have to go through all of that and work out where she's been," she said.
The woman lives at Tarragindi and visited Woolworths Annerley from 10.36am till 11.36am on Monday and Chemist Warehouse Annerley from 8.39am to 8.49am on Wednesday.
Authorities are waiting for tests to reveal what COVID-19 strains the three cases have contracted, and where they picked up the virus.
"I suspect we have got definitely one totally new outbreak, and potentially a second," Dr Young said.
She revealed that South Korean authorities informed Queensland Health about a passenger who tested positive after arriving from Brisbane last week.
A public health alert was issued on Wednesday for potential exposure venues at North Ipswich, Inala and at the Brisbane Airport on July 9.
Ms Palaszczuk has urged any Queenslanders in Victoria and regional NSW to return to the state amid outbreaks in both states.
The premier said people planning any trips to the southern states should not go.
"I cannot be clearer. We are seeing these little spot fires happening across the nation and we need to make sure we get this under control," she said.
Queensland reported two COVID-19 cases in hotel quarantine on Thursday.
Australian Associated Press