The girl, who lives at Taringa and goes to Indooroopilly State High, became unwell yesterday and tests overnight revealed she had COVID-19. The timing meant she would have been infectious in the community for three days, including two days at the school of around 2,500 students.

Queensland Health notified the school after midnight, prompting an email to parents cancelling today’s lessons to allow for deep cleaning and contact tracing. It is unclear how the girl normally travels to and from school, what extra-curricular activities she is involved in, and whether she had contact with students from other schools.

The girl has been taken to hospital and family members isolated while further tests are undertaken. They are not believed to have travelled to any hotspots.

Genome sequencing will hopefully shed more light on the latest mystery case, which Young said was “quite concerning because I’m struggling to understand how she’s acquired it”.

But Young reiterated Queensland had “13 incursions of the virus” in six weeks and it could possibly be linked to any one of them.

“In any particular outbreak, someone can get infected, not have symptoms and then spread the virus to someone else,” Young said.

With 43 active cases in Queensland, most now in hospital, Young urged people to get vaccinated and keep social distancing and wearing masks.

Deputy Police Commissioner Steve Gollschewski said there would be an increased police presence in areas of south-east Queensland where people have not been wearing masks.

He also urged the thousands of people in home quarantine to follow the rules, after a person was fined for visiting their elderly mother.