Coronavirus cases in Western Australia have surged by 17 and the source of infection for most is unknown, with the health minister saying it's clear community transmission is now occurring.
It is WA's biggest one-day spike and brings the total to 52.
Health Minister Roger Cook said it was not known where 12 of the new cases were contracted.
"We are now starting to see the emergence of community-based transmission of the virus," Mr Cook told reporters on Thursday.
"We always knew that this would happen and we're prepared, but it is now obviously appropriate for us to respond by elevating plans the Department of Health has."
Two of the new cases are healthcare workers.
One of them, a physician, worked at Fiona Stanley Hospital and also St John of God Hospital's Ursula Frayne ward. He was asymptomatic on Monday but developed a dry cough that night.
The physician had contact with three patients and 13 colleagues at Fiona Stanley Hospital.
Contact tracing is underway for 12 Ursula Frayne patients, which is a secure mental health ward for older adults, and one patient in a rehabilitation unit.
The other infected healthcare employee is a nurse who returned from overseas on Monday and did not go to work, immediately self-isolating.
The state's first regional case, in the southwest, is among the 17. Three are in hospital in a stable condition.
Earlier on Thursday, Premier Mark McGowan told parliament society needed to continue as normal for as long as possible.
"You do not close down offices, factories, construction sites, mines unless it is an absolute last resort," he said.
"Otherwise our economy will suffer grievously, thousands upon thousands of people will go bankrupt, our health services will suffer, our schools and our children will suffer.
"You do not do it lightly."
WA Secondary School Executives Association president Armando Giglia told AAP the absentee rate at high schools was currently around 15-20 per cent, double the usual rate.
The State School Teachers' Union of WA is calling for action to protect the health of staff and students, including a significant increase in cleaning hours, and swift re-stocking of soap and hand sanitiser.
The unions said it expected any teacher in a high-risk group, either due to age or underlying health conditions, would be allowed to take leave or work from home.
The University of WA, Curtin University, Edith Cowan University and Murdoch University are introducing online lectures.
All Sunday services at the main Anglican cathedral in Perth, St George's Cathedral, have been suspended indefinitely, with Archbishop Kay Goldsworthy saying it attracts very large congregations and many tourists.
Australian Medical Association WA president Andrew Miller wants the government to advise the public of its plan, saying that will reduce anxiety.
"Tell us what you know ... what are the measures that we're going to introduce and what will trigger that?"
Australian Associated Press