Perth has been plunged into a five-day lockdown after a confirmed case of Covid-19 went to various locations the community.
WA Premier Mark McGowan held an emergency press conference on Sunday afternoon, saying a male security guard aged in his 20s had been working at Sheraton Four Points in the CBD where there were four active cases, including two of the UK variant and one of the South African mutant strain.
He had tested negative on January 15, 17 and 23 but developed symptoms on Thursday.
"Exactly how the infection was acquired remains under investigation," McGowan said.