A man working at a Perth hotel used for quarantining international arrivals has contracted the coronavirus, as another 200 people on Rottnest Island prepare to return home.

WA premier Mark McGowan said the man, 47, was a contact of someone who was in quarantine at the Pan Pacific Hotel and contact tracing was underway, issuing a warning of how COVID-19 remained “extremely contagious”.

“You’re never going to know where there’s going to be someone acquire the illness, which I think perhaps explains to everyone why we’re being cautious,” he said.

“We do need to continue to treat the issue seriously and I thinks this case arising, in an environment where we have had a number of days of zero cases, reminds us we’re not out of the woods yet.”

The latest case takes the state’s number of confirmed cases of the coronavirus to 553.

More than 200 people who have been quarantining on Rottnest Island will return to the mainland on Wednesday with the island remaining available for COVID-19 quarantining.

Up to 800 international cruise ship passengers who arrived in Perth throughout late March and April, were placed into quarantine in hotels across Perth, placing pressure on the state’s health system and hotel staff workers.

One female doctor, who chose not to be identified, told the ABC on April 9 she was “thrown under a bus” by the WA Health Department after being tasked with caring for “hundreds of passengers” across two hotels while dealing with a lack of personal protective equipment.

Meanwhile, Mr McGowan admitted he did not have the exact details about the man’s role at the hotel, but said all safety protocols had been adhered to.

Mr McGowan also defended his government’s COVID-19 road map for easing restrictions after some businesses expressed disappointment that they could not yet open while others could.

The premier said it was not possible to reopen everything at once.

“We had a new infection today and everyone was expecting no infections,” he said.

“We’ve been more forward leaning, more progressive, we’ve opened up more than any other state in Australia by a long way.

“But you just need to exercise some caution to make sure we don’t overstep the mark and then we have a spike in infections and we have to shut everything down again … that would be devastating.”

Four patients remain in hospital, including one in intensive care.

-with AAP