Health authorities have confirmed Australia has 100 confirmed cases of coronavirus lost as drastic quarantine measures are introduced in Europe.

The latest escalation in the number of Australians testing positive comes as Italy takes the unprecedented move to introduce lockdown measures across the entire country.

Australia’s chief health officer Professor Brendan Murphy told a press conference on Tuesday afternoon Sydney had “significantly the biggest part of our outbreak” in the country.

“We have continued to have some cases that have come from contacts of imported cases, some continued cases imported from a range of countries, and some additional cases from the community transmission event that’s happened in northern Sydney,” he said.

However, when asked whether Australia should follow Italy and have a complete shutdown of schools and universities and quarantine for 14 days, Professor Murphy said that decision would be made if there was more “sustained” community transmission.

“If we had more sustained community transmission, then we wouldn’t hesitate to make recommendations about public gatherings, schools and the like. We only had that one issue of community transition in Ryde,” he said.

Earlier, Italy’s Prime Minister Giuseppe Conte signed a decree on Monday local time restricting people to remain inside the areas where they live, restricting their movements in public spaces, restaurants and the transport system.

He said there won’t just be a “red zone”, referring to the quarantine order he signed for a vast swath of northern Italy with a population of 16 million over the weekend.

“There will be Italy” as a protected area, he said.

The latest developments come the Australian government follows the US in advising its citizens to “reconsider” taking an overseas cruise as the coronavirus outbreak continues to spread around the world.

“Australians, particularly those with underlying health concerns should reconsider taking an overseas cruise at this time due to COVID-19,” the Department of Foreign Affairs and Trade said on its SmartTraveller website.

“This is obviously a very significant development,” federal Treasurer Josh Frydenberg said on Tuesday.

“It just reflects the uncertainty and the seriousness of the spread of the coronavirus.”

A staff member at Melbourne private school Carey Grammar tested positive to COVID-19, forcing the closure of the school on Tuesday. Photo: Facebook

Overnight, there have been another eight new infections in NSW as parents and teachers from two schools wait to find out whether students can return on Wednesday. Another 600 tested awaiting results.

In Victoria, the state’s coronavirus help hotlines crashed due to an influx of calls.

Federal Health Minister Greg Hunt told reporters on Tuesday up to 20,000 around the country had contacted the hotline for advice.

The state’s dedicated COVID-19 phone line and the Nurse-On-Call Hotline have crumbled under the pressure “experiencing system issues due to extraordinary call volumes”.

“We thank the community for their patience as we work to increase the capacity of the hotlines – including putting on additional staff,” Ambulance Victoria said on Tuesday.

Tweet from @DrMukeshH

While the phone lines crashed, one Melbourne doctor resorted to seeing patients in their cars.

Former Australian Medical Association president Mukesh Haikerwal puts on a moon suit, mask and shoe covers before meeting patients outside his Altona North clinic.

After calling ahead, patients drive to the car park and remain in their vehicles before Dr Haikerwal comes out to take a swab while protected from transmitting the disease.

“They park outside the building and we go out one entrance that is okay to go out of to do the swabs, collect the swabs and they can go off and self-isolate until their result comes back,” Dr Haikerwal told 3AW radio on Tuesday.

“We go to our flu area and clean up all of our dirty garb… We are clean, they are clean. And nobody is contaminating the waiting area of rest of the practice, so it is clean.”

The makeshift car park clinic is the first of many expected to open in the coming weeks at car parks and open spaces, near medical practices across Melbourne.

The federal government has flagged funding the drive-through COVID-19 testing sites at up to 10 Victorian medical clinics, Australian Medical Association Victorian president Julian Rait told 3AW on Tuesday.

A teacher who tested positive for the virus sent elite private school, Carey Baptist Grammar School, in Melbourne’s east into shutdown.

The school closed to staff and students on Tuesday, initially over fears of symptoms consistent with COVID-19 before testing positive overnight.

The teacher was in direct contact with someone who has coronavirus, and the school is working with the health department to map the potential spread of infection.

A Melbourne Assessment Prison inmate is in isolation after being in contact with someone who tested positive for the virus, but no other prisons have been affected, Corrections Victoria said.

Victorians keen for information on the virus can visit www.dhhs.vic.gov.au/coronavirus.

-with AAP