Officers from Thursday, March 26, will have the power to issue fines of $1000 to individuals and $5000 to businesses that breach public health orders or ministerial directions, Police Commissioner Mick Fuller announced on Wednesday.

People in the firing line include returned travellers who contravene the requirement to self-quarantine for 14 days and those diagnosed with COVID-19 who similarly don't follow the rules.

Fines will also apply for breaches of the prohibition on outdoor gatherings of 500 people and indoor gatherings of 100 people.

"It's unfortunate it's come to this," a Hunter Valley Police District spokesperson said.

"But, people need to start listening to the expert advice."

It follows the passing of legislation in the NSW parliament on Tuesday to help tackle the spread.

Under the bill, police will be able to arrest people reasonably suspected of breaching COVID-19 public health orders and return them home or to a place of detention.

It comes after a two-month-old boy and a seven-year-old girl became the first children under 10 to contract COVID-19 in NSW.

The children both had contact with people with coronavirus, NSW Chief Health Officer Dr Kerry Chant said on Wednesday.

Meanwhile, the NSW branch of the Australian Medical Association says employers are being "grossly irresponsible" and wasting doctors' time by sending employees to get clearance and sick leave notes during the health crisis.

Branch president Dr Kean-Seng Lim has told employers and schools to stop wasting health resources.

"I'd like to hang up a sign at my surgery telling people that I will not sign sick leave forms or provide someone with a note saying they don't have COVID-19 during a pandemic," Dr Lim said in a statement on Thursday.

"I would also like schools to do the same with students, please."

He said everyone should make the best use of the health system "because we are at a point where we are about to need every possible efficiency we can get".

By Wednesday there were 1029 confirmed coronavirus cases in the state. Of those, about 500 people contracted the disease while overseas.

Premier Gladys Berejiklian said the public needs to step up to slow the spread of the virus which has so far killed nine people in Australia, including seven in NSW.

She backed new public restrictions announced by the prime minister on Tuesday night to control the spread of COVID-19.

"This is a time that all of us have to step up," Ms Berejiklian said.

"We need to make sure the community does the right thing by yourself, your family and others."

The premier said there will be thresholds in place allowing NSW to take further action, separate to other states, once the number of community transmissions reaches a set amount.

Planning Minister Rob Stokes on Wednesday said usual planning controls restricting trading hours had been scrapped to allow for round-the-clock trading for supermarkets and pharmacies to make it easier for consumers to buy food and medical supplies.

Australian Associated Press