Public Health director Mark Veitch says he would not be surprised if another coronavirus case emerged in Tasmania, linked to a COVID-positive teenager.
A 15-year old Newnham boy, who flew into the state from Victoria on Friday, remains in a clinically well condition at a COVID case management facility in Hobart with his father.
Acting Premier Jeremy Rockliff on Tuesday said negative coronavirus test results had been returned for nine of the 17 close contacts of the boy.
He said the boy's father had not yet tested positive for COVID-19.
The close contacts include 10 passengers on Virgin Australia flight VA1364, family members, and airport employees.
Mr Rockliff said 35 casual contacts of the boy had all returned negative results.
The boy broke quarantine rules on Saturday, before being diagnosed with coronavirus, when he visited an IGA supermarket in Newnham.
He was there for a few minutes, but an exposure window has been declared by Public Health of between 2.20pm and 2.45pm.
Mr Rockliff said the supermarket was safe for people to visit.
Dr Veitch said it was confirmed the boy had contracted the Delta strain of COVID-19.
"The likelihood of a case amongst close contacts or at least one of the close contacts is quite high," he said.
"The people who he travelled with from the airport, his father, the relatives with whom he interacted before his diagnosis was known - he spent quite a time quite close to them.
"I would not be surprised if we get a case diagnosed amongst them either in the round of testing we're doing at the moment when it's complete or in the subsequent round of testing."
Dr Veitch said outbreaks of COVID-19 could occur until vaccination rates reached a high level.
"Even those parts of Tasmania that enjoy relatively high first and second dose vaccination coverages are currently at risk," he said.
"That's why we need to push the message for everyone statewide to get vaccinated.
"At the moment, nowhere in Tasmania is quite at the level that the vaccination coverage would stifle the spread of an outbreak."
Mr Rockliff said Tasmanians had undertaken 510 tests on Saturday, 499 tests on Sunday, 740 tests on Monday.
Mr Rockliff said 12 wastewater testing sites have been added to a testing regime in Launceston over the next two weeks.
Tasmania had not recorded a COVID case for 58 days until recently.
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