Metropolitan Perth and the Peel region will go into a three-day lockdown from midnight on Friday after a hotel quarantine outbreak led to community transmission.
Premier Mark McGowan says the lockdown is a necessary measure after two people, including a man who stayed in the hotel and completed quarantine before flying to Melbourne, spent days in the community while infectious.
Anzac Day dawn services will be cancelled and all people in the affected regions must wear masks when leaving their homes from 6pm on Friday.
“I know this is hard to take and I wish we didn’t need to be doing this,” Mr McGowan told reporters.
“But we can’t take any chances with the virus. We just can’t.”
A Victorian man tested positive for COVID-19 after travelling from hotel quarantine in Perth to Melbourne earlier this week.
Mr McGowan revealed the man may have been infectious for five days in Perth.
The man arrived in Melbourne on Wednesday and was advised upon arrival he was a close contact of a positive case in the hotel.
Victorian Health Minister Martin Foley confirmed the man returned a positive test on Friday morning, ending the state’s 55-day run of zero locally transmitted cases. He has been in isolation since arriving in Victoria.
“Public health actions are already underway, household contacts were urgently tested this morning,” Mr Foley said.
“This is an important and timely reminder this global pandemic is not over.”
Health authorities are working to contact other passengers on Qantas flight QF778, who are required to get tested and isolate for 14 days.
The man has three household contacts – his spouse and their two children, who were tested on Friday morning.
Mr Foley said the man wore a mask while on the flight and travelling through the airport. He said he was not aware of how many people were aboard the flight.
“We will be examining those movements for contact tracing purposes and for the purposes of establishing should there be any exposure sites,” he said.
It comes after West Australian health authorities on Thursday revealed there had been virus transmission in the Mercure Hotel Perth, which is being used to quarantine returning overseas travellers.
Two guests staying in rooms opposite each other tested positive for the virus and were later linked through genomic sequencing, the health department said in a statement.
Other guests who stayed on the same sixth floor at the same time were previously released from the hotel after testing negative.
Mr McGowan on Thursday said the Mercure Hotel would no longer accommodate returned overseas travellers.
With additional reporting by AAP.