A young consular staff member who tested positive to coronavirus in Queensland was infectious on a domestic flight after returning from overseas.
The man, who is in quarantine, was the state's only confirmed case on Sunday from more than 13,700 tests over 24 hours.
He flew into Maroochydore from Sydney on Friday on Jetstar flight JQ790.
Chief Health Officer Dr Jeannette Young said the man, in his 20s, was infectious on the flight and health authorities are tracing people who sat near him.
The man was allowed to take the domestic flight and quarantine at home as part of a select group of exemptions, Dr Young said.
"He did everything that he should have done... but it does mean that this is a risk," she added.
There are 13 active COVID-19 cases in Queensland and people are being warned to remain cautious.
"We are very comfortable with the figures overnight, but that next week is very crucial," Premier Annastacia Palaszczuk said.
"We are in a little bit of uncharted waters at the moment."
The state government has tightened restrictions on aged care homes in southeast Queensland as a precaution.
Visitors will no longer be allowed at facilities in Brisbane, Ipswich, Logan, Redland, the Gold Coast and the Scenic Rim, with exemptions for end-of-life.
Meanwhile, 104 residents at a Brisbane nursing home have returned negative test results.
It was confirmed on Saturday a woman who works at the Bolton Clarke aged care facility at suburban Pinjarra Hills had tested positive.
One resident was unable to be tested but Dr Young said there was no cause for concern.
The resident will be quarantined for a fortnight and monitored, she said.
The home had been locked down after the worker's husband tested positive on Friday.
He is believed to have contracted the virus at Sunnybank's Madtongsan IV Korean restaurant, which was attended by an infected woman who allegedly failed to declare a recent visit to Melbourne when returning to Queensland.
She is one of three women - two of whom have tested positive - charged with fraud and lying to health officials.
Queensland closed its borders to travellers from Greater Sydney at 1am on Saturday morning, with Queenslanders returning from the region having to isolate in self-funded hotel quarantine.
Victoria recorded 671 new cases of COVID-19 on Sunday, its second-highest daily total, as tough new restrictions including a night-time curfew were imposed on metropolitan Melbourne.
NSW recorded 12 new COVID-19 cases on Sunday. State health authorities updated mask usage recommendations to include public-facing workers, worshippers and residents near clusters.
South Australia has recorded two new cases, one a young woman who attended a school while likely infectious. The state has warned of the potential for tougher protection measures. The woman was a close contact of a known COVID-19 case and has been placed in hotel quarantine.
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