The returned overseas traveller has been placed back into quarantine after producing a positive test result while in the community at the weekend.

Authorities are confident the man, who had been staying at Perth's Pan Pacific Hotel, is shedding viral particles and no longer infectious.

It emerged on Monday he had not been required to undertake a day 13 pre-clearance test.

The state government had announced last month that all returned travellers would be tested on days one, five and 13 during their 14-day hotel quarantine stay.

"Previously, all cases were cleared of their infection based on the national guidelines, which does not always involve a test prior to completing their isolation," WA Health said in a statement on Monday.

"A pre-clearance test will now be performed on all cases."

Premier Mark McGowan said he had only learnt at the weekend that the day 13 tests were not being rolled out for all guests.

"That was a surprise to me," he told reporters.

"I requested that that happen and that is now happening."

WA could soon go a step further and require all returned overseas travellers to undergo a fourth test on day 17 as a further precaution.

"That's an analysis we're currently undertaking," Mr McGowan said.

The maritime worker had been required by his employer to get tested upon leaving quarantine before boarding a vessel.

After completing his 14-day quarantine period on Friday, he stayed at the Ibis hotel in Perth, ate at a restaurant and visited an Optus store and a pharmacy.

He was put back into hotel quarantine after returning a positive PCR test on Saturday morning.

The man had been vaccinated and wore a face mask while he was out in the community. He did not have a variant of concern and has remained asymptomatic.

"The very strong medical advice is that he is a very, very low risk of being a spreader of the virus," Mr McGowan said.

WA Health has identified 33 casual contacts who have been asked to get tested.

The man had originally tested positive on May 21 after arriving at the Pan Pacific from Colombia via the United States.

He is the same man - identified by WA Health as Case 1017 - who infected a guest in an adjoining room at the hotel last month.

WA Health is yet to determine how the virus spread between the two rooms.

The state government will on Tuesday unveil details of its vaccine rollout for over-40s and allow them to book appointments for the first time.

Almost half a million doses have so far been administered in WA, with about three per cent of adults fully vaccinated.

Australian Associated Press