Three more people have been diagnosed with coronavirus in Western Australia as the state government released its updated pandemic plan on Wednesday.

The two men and one woman from Perth who have tested positive had separately travelled to Europe, the UK and US.

Patients outside the newly opened COVID-19 fever clinic at Royal Perth hospital. Credit:Shannon Smith

They are all stable and in home isolation, chief health officer Andrew Robertson said on Wednesday.

He said some developed symptoms on their return to Perth and some while they were on the plane.