Restrictions will remain in place until at least Friday night,with Mr McGowan flagging West Australians may have to get used to wearing masks.

Health Minister Roger Cook said the ‘working theory’ as to how the security guard became infected was that a returning traveller from the US passed the virus on to the man,as well as another traveller from Indonesia.

Genome sequencing has revealed the three people have the US variant of the virus,with the two travellers arriving on the same plane.

“[The two travellers] arrived on the same day and they were cohorting on the same floor of the hotel so you can imagine a couple of opportunities where it might have had the opportunity to transfer,” he said.

He said the hotel’s lift and its buttons were being explored as a potential exposure event,with CCTV being reviewed.

The hotel’s ventilation is not believed to have contributed,with the rooms the infected cases were in negatively or neutrally pressured.

Mr McGowan said the transmission between the two guests likely occurred on the aircraft. How one of them then infected the guard remains under investigation.

Perth avoids lockdown for now

Mr McGowan said a lockdown had so far been avoided because – while case 1001 was suspected of being in the community for four days while potentially infectious – it had occurred while some step-down restrictions were still in place from the Mercure Hotel outbreak.

The hotel security guard had days earlier received his first jab of the COVID-19 vaccine,initially believing his symptoms to be as a result of the injection.

From May 10,vaccines are due to become mandatory for COVID-19 frontline workers.

Australian Medical Association president Omar Khorshid told Radio 6PR the repeated breaches in hotel quarantine in WA had been frustrating.

“It appears to us not every step that could have been taken to avoid these breaches has been taken by WA and some other states,” he said.

“I think Premier McGowan needs to stop avoiding responsibility and just do everything that he can do to protect the workers that are in hotel quarantine.

“There shouldn’t be anybody there who is not vaccinated,and this chap was not fully vaccinated. They should be wearing appropriate PPE which,from what we understand,is not currently the case.”

Despite an independent review of WA’s hotel quarantine system,provided to the state government in April,recommending N95 masks be worn by security guards outside isolating rooms,WA Health has decided against adopting the suggestion,as it says the masks are too uncomfortable to wear for extended periods.

Vaccinations now available for anyone over 50

From Monday,anyone over the age of 50 is eligible to receive the AstraZenaca vaccine.

Mr McGowan and health minister Roger Cook were among the first in line to receive their jabs at the Tom Wilding Pavilion at Claremont Showgrounds.

The vaccine is available at government-run vaccination clinics. Regular GP clinics will able to provide the shot from Monday,May 17.

Bringing the vaccine forward for people aged 50 and over means almost six million Australians not yet vaccinated in the 50-69-year-old group will now be eligible.