The man was a close contact of another case, with whom he shared a bathroom.
"It is believed he has been infectious in the community, so therefore there are further exposure sites," Premier Mark McGowan announced on Thursday.
Those sites are Dominos Pizza in East Fremantle on December 28, BP on Queen Victoria Street in Fremantle on the same day, an O'Connor climbing gym the day before and Farmer Jack's Spearwood on December 26.
The 27-year-old brings the cluster connected to a French backpacker to 13.
The Frenchman flew from Queensland to Perth before the border tightened and went to a Perth Mess Hall dance party 10 days ago.
Western Australia has also escalated its COVID-19 pandemic response with tougher border rules, tightening entry requirements for Queenslanders and South Australians.
Queensland recorded 2222 cases on Thursday, while an infected child under the age of two has died in South Australia as the state reported another 1374 cases.
From Friday at 6pm, both states will be deemed 'extreme risk', with travellers not permitted into WA except in extraordinary circumstances.
Mr McGowan said the decision was based on both states recording significant COVID-19 case spikes in recent days.
"My advice to any Western Australian that has an approved G2G pass and wishes to return home from those jurisdictions is to do so immediately" Mr McGowan told reporters on Thursday.
Under the extreme risk classification, travel exemptions will only be approved for Commonwealth and state officials, members of parliament, diplomats, and people who perform specialist roles.
Extraordinary circumstances entry applications will be assessed by WA Police or the chief health officer.
All approved travellers must be double-dose vaccinated and have returned a negative PCR test in the 72 hours before arriving in WA.
They must also undertake hotel quarantine at a state-run facility for 14 days at their own expense and get tested for the virus on days one, five and 13.
WA's first-dose vaccination rate climbed to 91.7 per cent for people aged over 12, and 83.6 per cent for two doses.
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