A Victorian doctor who treated more than 70 patients after falling ill is the state's latest victim of the coronavirus, as another six cases 19 were identified in NSW.

Australia now has 70 confirmed cases of COVID-19, with two deaths and 22 who have recovered, the nation's deputy chief medical officer says.

"Most of the cases we have had so far, luckily at this point, have been quite mild, so the symptoms have recovered much quicker," Professor Paul Kelly said on Saturday.

The virus has spread to more than 90 countries.

An extra 260,000 masks will be immediately released from the federal stockpile to primary health networks, but doctors and others can ask for them too, Prof Kelly added.

The Victorian doctor's diagnosis has prompted concern for those he treated at The Toorak Clinic in Melbourne. His patients, along with staff, are required to self-isolate.

Two patients he visited in Malvern's Mecwacare nursing home are also in isolation.

"I'm absolutely flabbergasted that a doctor who has experienced flu-like symptoms has presented to work," Victoria Health Minister Jenny Mikakos said on Saturday morning.

"I understand it was very mild symptoms - perhaps he didn't make the potential link - but we've now got 70 patients that have been contacted, so it is incredibly important that all healthcare workers take this matter very seriously."

Prof Kelly had a message for unwell people, especially workers: "Don't soldier on."

The doctor, aged in his 70s, is believed to have contracted COVID-19 in the US state of Colorado. He showed symptoms while returning to Melbourne via San Francisco on February 29.

People are urged to go about their lives as normal - without hoarding food or toilet paper - as the health department can organise supplies for those caught short by self-isolation.

The NSW government on Saturday announced six new cases of COVID-19, bringing the state total to 34.

All of the new cases were close contacts or family members of previously confirmed cases, except for a male who contracted the virus after visiting Italy.

NSW health authorities are tracking down passengers on a Qatar Airways flight from Doha after a man in his 70s was among the six new cases.

A Sydney school may also close for a fortnight after a male student, 16, tested positive.

Prime Minister Scott Morrison on Friday estimated the coronavirus outbreak could cost Australian taxpayers about $1 billion in health spending.

He announced a special shared funding deal to help states and territories shoulder hospital, health service and other response costs.

Epidemic planning talks were held on Friday for the aged care sector while Queensland considers scenarios to decide the threshold for drastic measures, such as school closures.

Meanwhile, four more Australians have been caught up in yet another cruise ship emergency, this time off the coast of California.

Twenty-one passengers on board the ship have tested positive for the coronavirus.