Authorities on Friday revealed a woman who flew into Perth from NSW without a valid travel pass earlier in the week had tested positive. She was rejected entry to WA and directed to hotel quarantine where her infection was confirmed.

Premier Mark McGowan said the flight's other passengers were all in quarantine and the infection was not expected to impact Saturday's grand final.

More than 60,000 fans are set to attend the clash between Melbourne and the Western Bulldogs at Optus Stadium.

Attendees are not required to wear masks or practice physical distancing.

Another infection was detected this week in a truck driver who had visited from NSW but authorities are confident it's an isolated case.

The premier said the grand final would be a historic event for WA and he was "confident we will do the big match justice".

AFL chief executive Gillon McLachlan on Thursday said he wouldn't be fully relaxed until after the final siren is sounded, with WA having twice previously banned crowds at AFL games this season in response to cases being detected.

He added that he had "great faith" in the WA government given the state's success in preventing any major virus outbreaks.

"We leave it to the people who know what they're doing and take their advice, and I think the premier's given a pretty detailed assessment of where everything sits," he said.

"We're confident and excited."

Australian Associated Press