Brisbane’s COVID-19 outbreak has swollen to 47 cases with the state’s chief health officer warning that the state is on the verge of a “large outbreak”.

The 16 new cases announced on Tuesday are all linked to the west Brisbane Delta cluster, which has grown from one to 47 cases in four days.

A 17th case was recorded in Cairns on Tuesday, but authorities are trying to determine whether it is infectious or historical.

Chief health officer Jeannette Young said the 34,718 tests conducted overnight were encouraging, but she still wanted 40,000 a day.

She urged people in the 11 locked-down local government areas in the state’s south-east to stay home until shutdown orders are scheduled to lift on Sunday.

“Please don’t move the virus,” Dr Young said on Tuesday.

“Wherever you are in those 11 LGAs, if you can at all, just stay put so that that virus then doesn’t move, because we know that there are people out there who could have been infected, who have no symptoms.

“The best way to deal with someone who has no symptoms is that they just stay at home. That’s why lockdowns work, because we know that the virus can burn out. So please just stay at home.”

Deputy Police Commissioner Steve Gollschewski said 70 infringement notices were issued and 21 people were arrested overnight.

He said police would install RBT-style roadblocks to enforce the hard lockdown.

“We’ll start RBT-type stops at intersections to check if people are allowed out for a valid reason,” Mr Gollschewski said.

“There is nothing to fear if people are doing the right thing.”

Dr Young has previously advised younger adults not to get the AstraZeneca vaccine, but she admitted that was set to change.

She said under 60s who felt they were at risk should speak to their GPs about that vaccine.

The Commonwealth is sending another 150,000 doses of AstraZeneca to the Queensland after declaring the south-east as a hotspot.

Dr Young said her advice that 18-year-olds shouldn’t get AstraZeneca would change if the cluster grew further.

“The ATAGI advice says when you reach a large outbreak – which I think we’re on the verge of, I hope it doesn’t become any larger, but I suspect it will – then that is the time,” she said.

One new case on Tuesday was linked to Indooroopilly State High School, four to Brisbane Grammar School, two to Brisbane Girls Grammar, three to Ironside State School, five are household or family contacts and one is a neighbour.

Nine of the 16 new cases are children and some have been infectious in the community for six days.

Dr Young said 7995 people were in home or hotel quarantine, including more than 400 health workers.

Some surgeries and outpatient services will be delayed, she said, because of staff shortages.

“No Queenslander will be denied any care because the health workers they need are in quarantine, we’ll work through that,” Dr Young said.

Most of the quarantined health workers had been vaccinated, she said, but there was a risk of them passing on the virus to their patients.

Dr Young said the link between the original family that was infected and two overseas acquired cases who were treated at the Gold and Sunshine Coast hospitals was still unclear.

“There’s still missing cases between them, absolutely, but possibly not a large number, but we know even one case can lead to another outbreak,” she said.

-AAP