Greater Brisbane has been ordered into a three-day lockdown after a coronavirus cluster grew to seven cases with evidence of "significant community transmission".
Four new cases were reported on Monday, all of which are likely close contacts of three existing and historical cases.
Premier Annastacia Palaszczuk says the infected people have been out in the community and travelled to central Queensland and northern NSW.
To stem transmission, Brisbane, Logan, Moreton Bay, Ipswich and Redlands will go into a three-day lockdown from 5pm on Monday - an area with about 2.5 million people.
"I didn't sleep last night so I think I am very worried, I'm very concerned," Ms Palaszczuk told reporters.
"But we've done it before, we've got through this together, and I'm sure that if everyone does the right thing we will be able to get through it."
Ms Palaszczuk said the lockdown would be reviewed on Thursday, ahead of the Easter holiday break this weekend.
People will only be allowed to leave home to do essential work, shop, care for people or exercise.
Greater Brisbane schools and all non-essential businesses premises must close from Monday afternoon.
"This will also enable our health authorities to get on top of the contact tracing," the premier said.
"This is a huge job now that we have to do because we've got more of this community transmission."
It is the second Greater Brisbane lockdown this year after an earlier shutdown in January.
Anyone who has been in Brisbane since March 20 will also come under the lockdown restrictions.
One of the cases travelled to Gladstone and Gin Gin from March 25 to March 27 and two cases visited venues in Byron Bay in NSW on March 26 and March 28.
The premier said face masks would be mandatory in Brisbane, and will need to be worn indoors throughout the rest of Queensland.
All venues outside Greater Brisbane will only be allowed to host seated patrons.
Chief Health Officer Jeannette Young says four of the new cases are linked to two men in northern Brisbane and a Princess Alexandra Hospital doctor who tested positive.
Two cases are colleagues of a Strathpine man who tested positive on Friday night, while the other cases are a doctor, who tested positive on March 12, and her sister.
Dr Young said it was unclear where the transmission occurred and genomic testing on both latter cases was underway.
"We now have significant community transmission," she said.
States and territories have also moved to restrict incoming travel from Brisbane and the state.
Western Australia will close its border to the entire state of Queensland from 1201am (WST) on Tuesday.
Tasmania has shut its border to Greater Brisbane travellers, while South Australia will do so from 4pm (CST) and Victoria closes to Brisbanites from 6pm (AEDT).
Anyone from Greater Brisbane must isolate and get tested upon entering the Northern Territory and the ACT.
In NSW, people who have been in the lockdown area since March 20 are now subject to the same stay-at-home restrictions as Greater Brisbane.
Entry declarations that ask for details of visits to venues of concern are required for Greater Brisbane arrivals, and NSW Health is advising against non-essential travel to the northern city.
Federal Health Minister Greg Hunt hasn't declared Brisbane as a hotspot yet, but the Australian Health Protection Principal Committee will discuss the situation on Monday afternoon.
However, he has authorised testing for people who are asymptomatic to help contact-tracing efforts.
"I have confidence in Queensland's ability to deal with this outbreak," Mr Hunt told reporters.
"I think they're in a strong position to protect Brisbane and Queensland and, thereby, Australia."
Queensland Health conducted 11,626 tests on 6130 people in the 24 hours to 9am on Monday.
The federal government has also agreed to halve the state's weekly intake of overseas travellers into hotel quarantine from the current 1300.
Australian Associated Press
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