Doomsday predictions are spreading untethered online, but experts say there are many ways the virus could play out.

There are fears an infected Sydney doctor may have spread the coronavirus to a large number of patients, after seven more people tested positive in NSW and another case has been confirmed in Victoria.

Forty staff members who work closely with the 53-year-old male doctor at Ryde Hospital have been isolated.

They include 13 doctors, 23 nurses and four other health workers. The infected doctor is in a stable condition at Westmead Hospital

However, authorities say the doctor had already come into contact with a “large and diverse” range of patients in his workplace.

“We still don’t know how he acquir­ed the infection,’’ NSW chief health officer Kerry Chant said.

“We are doing an investigation as we speak. He did not care for any of our positive cases but we are doing some additional investig­ations into what patients he saw, to see whether there were any undiagnosed cases.”

A further eight patients of the doctor are showing no symptoms, while 29 other patients identified as casual contacts are being chased up.

Sky News reports that one of the seven new NSW victims is a 50-year-old female aged care worker at a nursing home in Sydney’s north west.

It’s understood she did not leave Australia recently and is the third case of human-to-human transmission within the country.

Also this morning, a man in Victoria has been diagnosed with coronavirus after travelling to Australia from Iran, taking the national total of cases to 42.

Victorian Health Minister Jenny Mikakos says the man in his 30s became unwell on Sunday after returning to Victoria from Iran on February 26.

He went to an emergency department after speaking with a nurse on call, with his positive test result confirmed late on Tuesday.

Authorities are now struggling to track potential victims after it’s been confirmed one of the new cases is a human-to-human transmission inside Australia.

In that case, the virus spread to a NSW woman in her 50s had not travelled outside of Australia recently.

NSW Health is alerting passengers who were on five separate flights from Asia in the past week after two men in their 30s, a man in his 50s and two women in their 60s tested positive following their arrival in NSW.

The men in their 30s travelled from Iran, the two women flew from Japan and South Korea respectively, and the man in his 50s was returning from Singapore.

And health authorities are advising passengers who sat near a coronavirus- infected woman on a Doha-to-Sydney flight to immediately isolate themselves at home.

The woman in her 50s who flew into Australia from Iran on February 23 aboard Qatar Airways flight 908 from Doha was in seat 43H.

Another locally acquired case in Sydney is a 41-year-old sister of an infected man who recently returned from Iran where the virus is rampant.

As the hunt for virus victims ramps up state and federal authorities are clashing over the “tracing” measures used to find them, after NSW authorities say they’ve hit a stumbling block.

They are trying to get hold of passenger cards for people who sat on the high-risk flights near infected people, but say the process has been a struggle.

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Dr Chant has called on the federal government to introduce a “streamlined” way to get the details of those sat on the at-risk flights.

She said authorities were still waiting for the Australian Border­ Force to provide cards for people who sat near an infected woman who flew into Sydney on February 23 aboard Qatar ­Airways flight QR908 from Iran.

However, the federal government says there are no delays in providing health authorities with incoming passenger cards.

“We are making sure we get in contact with them and make sure they don’t have symptoms,” Mr Hazzard said. “It’s a bit of a worry.”

The latest infections bring total number of corona­virus cases in Australia to 42, with more people undergoing tests.

Across the globe, more than 90,000 coronavirus cases and 3100 fatalities have been confirmed, including the death of West Australia­n James Kwan.