Precautionary measures will be introduced at schools across Western Australia from today to manage the impact of coronavirus and try to restrict its spread.

Key points: Schools in WA are remaining open but large gatherings will be cancelled

Schools in WA are remaining open but large gatherings will be cancelled Assemblies, carnivals and concerts are among the affected events

Assemblies, carnivals and concerts are among the affected events Principals have also been told to stagger recess and lunchbreaks

It comes after a state of emergency was declared in WA in response to the outbreak, with Premier Mark McGowan yesterday saying extreme measures were being triggered in an effort to protect the community.

Schools across the state are remaining open at this stage, with parents told to send their children to class this morning as usual.

But education chiefs said a series of precautionary measures were being put in place, with students and staff who returned from international travel ordered to self-isolate for 14 days.

WA Education Department director-general Lisa Rodgers said sensible social distancing measures were also being introduced.

"From Monday, it is expected that principals will cancel or postpone all organised, non-essential gatherings of more than 500 people until further notice," she said.

"This includes swimming and sports carnivals, interschool carnivals, performances, concerts, exhibitions, fetes and fairs.

"Organised, non-essential gatherings of fewer than 500 people should be reviewed and reconsidered to minimise the spread of COVID-19."

WA director general of education Lisa Rodgers has ordered non-essential school gatherings be cancelled. ( ABC News: Rebecca Carmody )

Assemblies banned, breaks staggered

Ms Rodgers said in schools with more than 500 students, principals must change arrangements for assemblies and recess and lunchbreaks.

"Full school assemblies should no longer be held and principals are required to stagger recess and lunch breaks," she said.

"WA schools are following a national approach and will remain open unless authorised by the WA chief health officer to close.

"It's important we all work towards managing the impact and reducing the exposure of COVID-19, which is why these considered actions are being taken.

"These decisions have been made with the best interests of staff and students in mind.

"This is the situation as it stands based on current advice and we will continue to keep schools informed."

North Perth Primary School parent Sarah Smith, who works at Perth Children's Hospital, said she had concerns about people working in health care.

"I'm a nurse, so it makes it really difficult. If they shut down the schools, then obviously I can't go to work. The majority of my friends and colleagues, they all have kids.

"I just don't think as a long-term plan, I don't think they can shut down the schools and then expect parents to stay at home look after their kids — nothing's going to function."

Not 'anywhere near' closing schools: Premier

Mr McGowan said yesterday he understood there had been calls to close schools in WA, but he did not believe it was necessary yet.

"I don't think it is anywhere near that point at this time," he said.

"We have an agreement that we will monitor the situation, but if a child tests positive for coronavirus, that child would obviously need to self-isolate and at that time the school would have to close so we can test whoever has been in contact with that child.

"If absolutely necessary, we can rule out those online learning materials for families."

Premier Mark McGowan says he does not think schools need to close at this stage. ( ABC News: Nicolas Perpitch )

It was revealed yesterday one more West Australian had contracted COVID-19, bringing the state's total to 18.

Health Minister Roger Cook said the woman aged in her 60s tested positive after travelling overseas.

He said more than 5,500 tests had been carried out so far by GPs and at COVID-19 fever clinics, which opened in Perth earlier this week.

There has been no known community-based transmission of the virus to date in WA.

Anzac Day services cancelled across WA

All Anzac Day services and commemorations have been cancelled across Western Australia because of the coronavirus pandemic.

The RSL board met on the weekend and decided services could not go ahead, given the ban on gatherings of more than 500 people and concern over the health of elderly and vulnerable veterans.

RSL WA chief executive John McCourt said it was the first time since 1942, when there were concerns over Japanese air raids during World War II, that services had been cancelled.

"It's my melancholy duty to advise RSL WA has now cancelled the conduct of all Anzac Day commemorations as a result of the situation," Mr McCourt told ABC Radio Perth.

Anzac Day dawn services, which attract tens of thousands to places like Perth's King's Park, have been cancelled. ( Grant Wynne: ABC )

"Given that the Prime Minister's announcement that there was a banning of any public gathering of over 500 people, by simple mathematics that would mean the dawn service at Kings Park, the street parade in the CBD and the commemorative service in the Concert Hall are cancelled."

The RSL has also cancelled all commemorative services across the state.

"It's a blanket advisory. We can't legally tell people what to do, but there will be no RSL WA sanctioned or operated Anzac Day commemorations anywhere in Western Australia," Mr McCourt said.

"The health and wellbeing of veterans, especially our aged veterans — and there are a lot of them — is paramount."

Courts shut down some operations

WA's Supreme Court this morning announced all new jury trials due to start today would be adjourned until tomorrow due to concerns over COVID-19.

A decision will be made later today on whether they will proceed.

Jurors who arrived this morning were told to go home and asked to return tomorrow if required.

In a statement, Chief Justice Peter Quinlan said members of the public were requested not to attend court if they were not required to be there.

"Wherever possible, all directions hearings, case management conferences and strategic conferences will be conducted by telephone," he said.

Justice Quinlan said while civil trials would continue as listed, criminal trials were under review.

The high-profile Claremont serial killings trial is about halfway through its estimated seven months of hearings and is due to resume on Monday.

It is not yet clear how it will be impacted by the new arrangements.