Southeast Queensland will be plunged into another snap three-day lockdown from 4pm today as health authorities race to quash a new outbreak of Covid-19.
The announcement came as the state recorded six new community cases of the virus on Saturday, all linked to the 17-year-old Indooroopilly State High School student who tested positive to Covid-19 on Friday.
The new cases are the girl's four family members, a medical student who tutors the girl, and a staff member from Ironside State School where one of the siblings attends. They are all confirmed to have the Delta strain.
It's believed the student had been infectious and out in the community since July 27. She had been at school for two of those days.
Queensland Deputy Premier Steven Miles said the lockdown for 11 local government areas in the southeast of the state around Brisbane was "the only way to beat the Delta strain".
Residents will only be able to leave their homes for four reasons: to obtain essential goods, but only within 10km of their homes; essential work, school or childcare (with masks to be compulsory at high schools); to exercise within 10km of their homes; and for medical care.
The source of the outbreak remains unclear, however Queensland chief health officer Jeannette Young said one of two recently returned travellers had likely given it to an unidentified mystery link who had then passed it on into the community, and to the medical student who tutors the high school girl.
"I think that one of those two cases has led to transmission to someone – who I don't know – which has then led to further transmission and eventually I think the most likely scenario is this medical student has acquired it," she said. "I don't know how."
Young warned the public of the Delta strain's capability to spread and the need to respond quickly.
"We know from Sydney and here, indeed, as well that people transmit Delta in as quickly as 30 hours after they're first exposed," she said. "And that's why we need to have a particularly restrictive lockdown."
Thousands of people from Indooroopilly State High School and Ironside State School will undergo 14 days' quarantine.
The University of Southern Queensland Springfield Campus has also closed for deep cleaning following revelations that staff and students interacted with members of Indooroopilly State this week.
The virus "could be anywhere" in southeast Queensland, Young said, warning the public to remain on alert and only leave home when absolutely necessary.
"It could be in the Sunshine Coast, because we had one of those original cases up there, and they live in Buderim," she said.
"It could be down in the Gold Coast, because we had one of those original cases down there when they were being managed.
"So, I don't know today where this virus is in the southeast of Queensland. But wherever it is, I don't want it to go further."
An exposure concern has been flagged as far north as Townsville. Local rugby league games have been suspended this weekend.
"Due to a potential Covid-19 exposure within the Townsville Blackhawks, Queensland Rugby League has taken the precautionary steps to cancel this weekend's matches in Townsville against the Ipswich Jets until further notice," a statement read.
Brisbane residents have been urged to monitor the Queensland Health website, with exposure sites expected to be added over the weekend.