Health Minister Roger Cook confirmed on Sunday that the Patricia Oldendorff was en route to Indonesia's coal loading port of Tanjung Bara.

The vessel, carrying 20 Filipino nationals and the captain, arrived from Manila on September 16 and was anchored eight nautical miles off Port Hedland.

Eighteen of its crew members caught the virus but have now recovered.

WA Health said 12 of the recovered crew had returned to the vessel before setting sail, while three yet-to-be cleared colleagues were flown to Perth and now reside in hotel quarantine.

It comes as an unwell crew member aboard a Panama bulk oil carrier returned a weak positive test after coming ashore.

The Vega Dream anchored off Port Hedland on Friday after sailing from Shanghai via Manila, Mr Cook said.

It was taking on cargo on Saturday night when the man started to feel unwell. He was taken to the local hospital where he returned a weak positive result from initial fast-testing.

"His samples are now being flown to Perth so we'll be able to verify the results of that earlier test," Mr Cook told reporters on Sunday.

Mr Cook was unsure how many crew members were aboard but said no one else was suffering symptoms.

"We don't know at this stage if they collected extra crew at Manila," he said.

"But it's been at sail for many weeks - I think over 16 days now."

The Health Department on Sunday evening confirmed two WA maritime workers had boarded the vessel, but were deemed a low risk of infection as they had not come in to contact with the infected crew.

Mr Cook earlier assured the WA public the ship posed no health risk and it would leave the state's shores on Sunday.

"Those oil carriers come to rest a good 12 metres from the dock," Mr Cook said.

"We don't think there's any infection risk to any of the port workers or any of the community."

The Health Department confirmed the ship would leave the port after 5pm, but would anchor off the coast "for the time being".

There are no plans to send WA Health officials aboard the vessel to test other inhabitants until the crew member's initial test result is verified.

Mr Cook said the federal government had to make sure it works with its international partners to ensure "we don't have these situations continuing to emerge".

WA recorded two new cases on Sunday - a man and woman in hotel quarantine - as the state notched six months without any community transmission.

"It shows the measures we've used, including our hard border with the east, have worked," Premier Mark McGowan said.

Australian Associated Press