WA Premier Mark McGowan has taken the strictest approach out of Saturday's Australian Health Protection Principal Committee meeting, reimposing a "hard" border with all travellers from NSW.

Only those with exemptions - such as essential health and freight workers - will be allowed in after 12.01am on Sunday.

"This has been a difficult decision to make especially given the time of year," Mr McGowan said.

He criticised NSW health authorities for taking a "whack-a-mole" approach to the outbreak thus far.

"They seem to step on a gym here, or a restaurant there," he said.

"This is causing grief all over Australia so they need to kill the virus in NSW."

Victorian contact tracers have identified 70 primary close contacts of northern beaches cases among travellers who have arrived between December 11 and 17 and has flagged it may announce stricter border restrictions.

"We remain extremely concerned about the outbreak in NSW and the likelihood that it has seeded beyond the northern beaches," Health Minister Martin Foley said.

The state has had 50 consecutive days of no local virus transmission and authorities are desperate to protect the hard-won gains in the wake of its devastating second wave.

Tasmania's Premier Peter Gutwein raised the risk level for Sydney as a whole on Saturday, mandating that all travellers from Sydney must quarantine for two weeks on arrival.

The decision prompted organisers to cancel the Sydney to Hobart yacht race.

Queensland has reinstalled a border pass system and South Australia is requiring travellers from the northern beaches area to quarantine.

All jurisdictions are telling their own residents to reconsider travel to Sydney.

NSW recorded 23 fresh COVID-19 cases on Saturday, bringing the outbreak to a total of 40 cases.

Premier Gladys Berejiklian said she expected there to be the same number of cases or more recorded on Sunday.

There were already more cases being reported after the 24-hour reporting cut-off, which Ms Berejiklian said would be included in the Sunday count.

The premier also said there was a possibility of restrictions being imposed across greater Sydney on Sunday.

The community at the centre of the outbreak is in strict lockdown until Wednesday.

Acting Chief Medical Officer Paul Kelly commended northern beaches residents for self-imposing lockdown measures before they were officially announced on Saturday.

Ms Berejiklian praised the hotel industry, churches and other places of worship for closing before they were asked.

Genomic testing has indicated this particular strain of the virus came into Sydney via the US on December 1.

However it is not known how far the infection may have spread between then and December 10 and 11, when the virus strain appeared in three locations in the suburb of Avalon.

Health Minister Greg Hunt is calling for greater take-up of the COVIDSafe app over Christmas given that most Australians will be moving around more than at any time this year.

Australian Associated Press