Health officials in Queensland and Victoria say they are monitoring the outbreak in New South Wales amid concerns over the increased infectiousness of the Delta COVID-19 variant.
Two new local coronavirus cases have been reported in Brisbane, but the state government is more concerned about the risk posed by an outbreak in Sydney.
Chief Health Officer Jeannette Young says both new cases were in quarantine during their infectious period and being closely monitored.
There are now seven cases in the Brisbane cluster, all of which are believed to be the Alpha variant.
Six of those cases became infected after being in contact with a flight attendant at the Portuguese Family Centre in Ellen Grove and at DFO in Brisbane on Saturday, before the woman tested positive.
Dr Young says she's more concerned about people from NSW bringing the Delta virus variant into the state.
"We are continuing to see cases in NSW, so it is really important, that we could have a case in Queensland any day," she said.
"So please as Queenslanders have been doing for now the last 18 months if you have any symptoms at all, immediately come forward and get tested and isolate until you get a negative result."
Health Minister Yvette D'Ath said border declaration passes will become mandatory for anyone who has been in NSW, including border regions, from 1am on Monday.
Dr Young urged Queenslanders to reconsider plans to travel to NSW because infectious people from Sydney could be anywhere in that state and exposure sites could grow.
"People should really reconsider their need to go anywhere in NSW," she said.
"If it's urgent, unavoidable, of course they should travel, but if it's not perhaps they should think about holidaying in Queensland."
Meanwhile, Victoria has recorded no new locally acquired coronavirus cases beyond the two infections already announced by authorities.
The Health Department has confirmed the state recorded two local cases of COVID-19 in the 24 hours to Friday morning.
An Oakleigh man in his 60s tested positive on Thursday after returning from Sydney at the weekend and his co-worker at the Sandringham Dry Cleaners has also tested positive.
The Oakleigh man is believed to contracted the virus during a party at his daughter's house in West Hoxton in Sydney.
That Saturday night party has since been declared a super-spreader event.
The man returned to Melbourne on Jetstar flight JQ523, which left Sydney at 5.30pm on Sunday.
The flight has been listed as a tier-one exposure site, meaning anyone on board must get tested and isolate for 14 days.
The Sandringham dry-cleaning business has been listed as a tier-one exposure site and QR code data from the business is being analysed.
The man's only workplace close contact tested positive late on Thursday afternoon.
The second man's family has been isolated and members are being tested, with contact tracing underway.
The health department confirmed 21,991 tests were processed in the 24 hours to Friday morning, while 18,019 Victorians received a vaccine dose at one of the state-run hubs.
