All of the cases are in the southeast corner. So far there's been no order for a new lockdown.
The first case was reported late on Monday, an Eatons Hill man who works at an aviation training facility who was infectious in the community for three days. His wife is the second case.
The man was double vaccinated but only had his second jab a week ago.
Premier Annastacia Palaszczuk said there were significant concerns about the third case - the truck driver who was active in the community for a week while infectious, and who was staying in share accommodation.
"The police are speaking to this truck driver to get some more information from him," the premier told reporters on Tuesday.
The fourth case, which authorities are not too concerned about, was a person who tested positive after being released from two weeks of hotel quarantine.
The premier said masks have again been made mandatory in public settings in the Brisbane and Morton Bay areas.
"There's no need to panic because Queenslanders have been doing the right thing, especially in the southeast," she said.
Chief Health Officer Jeannette Young is due to address reporters shortly and will announce new restrictions on visits to aged care and disability care settings, and jails.
The aviation worker visited a McDonald's in Albany Creek, a childcare centre in Eatons Hill and stores in Rocklea and Aspley while infectious.
He has no recent history of overseas of interstate travel and authorities are probing the source of his infection.
It's understood the truck driver is the case linked to the Adalong Student Guesthouse in South Brisbane, a shared accommodation facility that's now under police guard.
The new cases come after 55260 people attended two NRL preliminary finals matches in Brisbane at the weekend.
Another 70,000 people attended the RiverFire festival on the Saturday night.