Victoria must reduce its coronavirus community transmission to virtually zero before Western Australia reopens its borders, the state's chief health officer says.
Plans to reopen WA's interstate borders on August 8 have been shelved amid a fresh outbreak of cases in several Melbourne hotspots.
There are now 288 active cases in Victoria, with 271 believed to have come from community transmission.
WA Chief Health Officer Andy Robertson on Monday said he wouldn't be advising the state government to reopen borders until Victoria's numbers significantly improved.
"If we look at Queensland, they haven't had any cases now for three or four weeks. NSW has had some, but they've got low levels," Dr Robertson told ABC radio.
"If either they've got no community spread or we're fairly confident that what little community spread (exists) is well under control and being effectively managed, that would be the time we would provide that advice (to reopen)."
WA recorded no new cases on Monday. The state has just four active cases, all in hotel quarantine and linked to overseas travel.
But with most restrictions on gatherings now lifted, Dr Robertson urged West Australians to maintain good hygiene practices.
"We have to realise that it can come back," he said.
"We are obviously protected to a degree by our borders ... (but) there's certainly quite a bit of traffic now on aircraft coming across from interstate."
He said COVID-19 could be reintroduced into WA and then, "given that we are reasonably open now, we could expect further outbreaks".
All people in hotel quarantine in WA are tested on day 12 of their 14-day quarantine period.
Dr Robertson said while authorities had the power to compel people in quarantine to be tested, they hadn't needed to use it.
"People have generally been very compliant," he said.
This comes as Victoria imposes mandatory testing on returned overseas travellers in hotel quarantine after it was revealed about 30 per cent were refusing to be tested.
Authorities are confident there are sufficient safeguards in place for the AFL's planned WA hub arrangement.
Collingwood and Geelong will meet at Optus Stadium on July 17 while serving 14 days' quarantine at Perth's Crown resort.
They will then each play West Coast and Fremantle before being replaced by another two Victorian teams, with the WA hub expected to continue on a rolling basis.
"If Collingwood and Geelong come here, it will be a secure quarantine arrangement," Premier Mark McGowan said on Monday.
"So they stay within the hub, they play each other within the hub, they don't mix with local people."