WA adds one backpacker-linked COVID case

The new infection is a woman in her 20s, in quarantine since December 23, who was a close contact of the index case, a 25-year-old unvaccinated man.

"This is good news and another encouraging result from this Delta outbreak," Premier Mark McGowan told reporters on Monday.

More than 600 close contacts have been identified with 86 yet to be located and tested, 39 of whom attended a busy 400-person event at Perth Mess Hall in Northbridge eight days ago.

WA police are attempting to find the outstanding close contacts so they can be isolated.

"This is something that is worrying because we cannot be 100 per cent sure that the Delta virus is not lingering in the community," Mr McGowan said.

The premier praised health workers at testing sites who have worked in scorching temperatures over the Christmas period.

He said their efforts, coupled with health restrictions limiting gatherings and a mask mandate, had yielded an "incredible" result and limited the spread of the virus.

"Given the high-risk nature of some of the exposure sites, we were expecting to see large numbers of positive cases," he said.

"But so far, we have limited the spread and now are in reach of possibly being able to kill off this outbreak."

However, Mr McGowan said WA remained at risk and the health restrictions would be extended to 6am on January 4.

"I'm sure that some people haven't got around (to getting tested for COVID-19) because they've got lots of events on and so forth," he said.

"Others may be worried they're then stopped from going to events or functions."

The premier also said there was little chance the WA border would be reopened before the planned date of February 5.

The new case brings the total number of locally acquired infections in the current outbreak to nine.

The index case visited nightclubs, shopping centres, restaurants and a cinema across multiple Perth suburbs after arriving in WA on December 12.