Sixty-nine staff and students from a school in Sydney's north have been told to self-isolate for 14 days after a student was diagnosed with coronavirus last week.

Key points: NSW now has 34 confirmed cases of coronavirus

NSW now has 34 confirmed cases of coronavirus One of the new cases is a man who recently returned from Italy

One of the new cases is a man who recently returned from Italy Passengers will continue to be screened at Sydney International Airport

Epping Boys High School was closed on Friday after a 16-year-old student tested positive for the virus.

The NSW Department of Education today said the school will reopen on Monday after being thoroughly cleaned.

But students and staff who have had close contact with the teenager have been told to self-isolate for 14 days.

The school is encouraging staff and students to stay at home if they become ill in the meantime.

It comes after the announcement of six new diagnosed cases of coronavirus in New South Wales today, bringing the total number of confirmed cases in the state to 34.

The Health Department said five of the new cases were either family members of people with the infection or who have been in close contact with someone already diagnosed.

The sixth person returned from Italy a week ago on Qatar Airways QR 908.

NSW Health said in a statement that 545 people are still being investigated and 6,217 have tested negative for the virus.

Authorities are continuing to screen passengers arriving at Sydney International Airport.

Sydney's northern suburbs yesterday emerged as the epicentre of the state's coronavirus outbreaks.

Three staff members from Dorothy Henderson Lodge aged care facility in Sydney's north have tested positive.

Four residents at the lodge have contracted the virus, and one of them, a 95-year-old woman, died earlier this week.

On Thursday parents and children were tested after a group of 17 children from the Banksia Cottage, at Macquarie University campus, visited the nearby Dorothy Henderson Lodge home on February 24.

The school, hospital, aged care facility and child care centre are all within about 4 kilometres of each other.

NSW Premier Gladys Berejiklian said the Government was "doing everything we can to reduce the spread of the virus".

"We are going to see cases escalate and we are going to see challenges in terms of decisions we take around how to contain and reduce the spread," she said.