Chief Health Officer Jeannette Young is scrambling to work out where the man picked up the virus as the list of exposure sites linked to him grows.
She says he either got it during a recent trip to China, in hotel quarantine in Brisbane, or after he was released on July 12 and went home to the Gold Coast.
The man, who was fully vaccinated, returned three negative tests while in hotel quarantine. However, he fell ill on July 15, three days after his homecoming.
AAP understands he did not seek a coronavirus test despite having symptoms.
It wasn't until he went to a GP eight days later, for an unrelated issue, that he got tested at the doctor's insistence.
Initial test results obtained on Saturday were inconclusive but a second test on Sunday was positive, forcing the man into hospital.
It's possible he could have spent a total of 12 days moving around the Gold Coast while infectious, including taking a child to and from daycare, eating out, and going shopping.
His family members were tested on Sunday but those results are yet to come back.
Dr Young is hopeful the risk is low but she has also noted the man's second test showed a higher viral load than the first, suggesting he could be at the start of his illness.
"There's so many unknowns here, so we're taking a very cautious approach ... and asking that people who've been to any of those sites contact us," she said.
She says anyone who has been on the Gold Coast or in Brisbane since July 13 should regularly check the growing list of exposure sites.
So far those sites include the Goodstart Early Learning centre at Parkwood, various dining venues, the Pacific Fair Shopping Centre and the Kmart store at Westfield Helensvale.
Meanwhile, police and contact tracers are still trying to piece together the movements of two other cases of concern - a Brisbane-based flight attendant and a New South Wales man accused of illegally leaving Sydney and travelling to Queensland with her.
Both are being investigated for breaches of health orders in Queensland.
Queensland police are also working with NSW counterparts over alleged breaches there.
The man is accused of flying from Sydney to Ballina on July 14, despite being told to quarantine because he'd been in close contact with a NSW case.
He wound up catching the virus and gave it to the flight attendant who drove to Ballina, picked him up, and then returned to Queensland where the pair was active in Brisbane and on the Gold Coast.
On Monday, Deputy Police Commissioner Steve Gollschewski said police had to resort to "formal" processes to get a direct interview with the flight attendant, who had brought in a lawyer.
When asked if she'd been cooperative, he said: "Not fully, not initially, no she wasn't."
"There are processes to get that information and we now have it," he said.
"We are now doing that with the male person."
He said some of the information provided to authorities had been proven to be incorrect.
"I don't believe we have a fine for lying to police, unfortunately."
Queensland recorded no new cases of COVID-19 in hotel quarantine on Monday.
The full list of Queensland exposure sites can be found at http://www.health.qld.gov.au/tracing
