The new cases of the Delta variant are all members of the same family who live across two households, including a 13-year-old schoolgirl from Sunnybank.

"There is no lockdown today," Premier Annastacia Palaszczuk said on Saturday. "We are very hopeful that we have been able to identify the source and get on top of this very, very quickly.

But the government may have to take "very quick, fast action" if it saw seeding outside the family in the next 24 to 48 hours, she said.

Aged care and disability care facilities, hospitals, and prisons in south Brisbane now have visitor restrictions and anyone with symptoms is being urged to get tested, as authorities work to make sure they are on top of the outbreak.

The most likely source of the virus is believed to be a visitor from NSW who stayed overnight at the home of the girl's father last Sunday.

The children were exposed to the visitor when they saw their father on Father's Day, then returned to their mother's home.

The man has since returned to NSW and has not yet been tested for the virus.

Queensland Chief Health Officer Jeannette Young thanked the children's mother for getting her daughter tested when she complained of a headache.

"This mum took her daughter to get tested simply on a headache," Dr Young said.

"That's what we want to see no matter how mild your symptoms, if you are unwell in any way whatsoever, don't hesitate."

The mother works at Griffith University and attended the Nathan campus on Wednesday, but saw "very few people", Dr Young said.

The girl's school, St Thomas More College at Sunnybank, was abruptly closed on Friday.

The exposure has sent about 1000 students, workers and families into home quarantine.

The new cluster emerged after a NSW truck driver tested positive, though the cases are not linked.

The truckie was infectious in the community at nearby Mount Gravatt and Archerfield on Sunday and Monday. He also visited Westfield Garden City shopping centre.

Other close contact exposure sites include a 7-Eleven in East Brisbane, a BP petrol station in Salisbury and an Acacia Ridge cafe.

There were 11,828 tests conducted and 23,631 vaccines administered in the past 24 hours, Ms Palaszczuk said.

Australian Associated Press