A person in northern California has contracted the coronavirus without travelling outside the United States or coming in contact with another patient known to have the infection, the first sign that the disease may be spreading within the community.

How the person acquired the respiratory disease is unknown.

"It's possible this could be an instance of community spread of COVID-19, which would be the first time this has happened in the United States," the Centres for Disease Control and Prevention said.

The infected individual is a resident of Solano County, which is home to Travis Air Force Base, where hundreds of Americans repatriated from China and others brought home from the Diamond Princess Cruise ship have been kept in quarantine. Many of them have been released.

Australia is the fourth-most prepared country in the world for a coronavirus pandemic, according to an analysis by Johns Hopkins Centre for Health Security. 

At his press conference today, President Donald Trump held up a graphic showing the US had the highest Index score of 83.5 by level of preparation to respond to an epidemic or pandemic.

Australia wasn’t far behind with a score of 75.5, below the UK and the Netherlands.

The researchers ranked 195 countries on their ability to prevent, detect and respond to health emergencies based on data from the Global Health Security Index.

Their report found international preparedness was "very weak" overall, with an avergae score of 40.2 out of 100.

Olympic legend Ian Thorpe is urging Australia's athletes to consider their long-term health before deciding to compete at the Tokyo Games.

As concerns mount over the spreading coronavirus, the Australian swimming great says Olympic organisers must ensure athletes will be safe at the Games due to start on July 24.

"I would most definitely be concerned," Thorpe told reporters in Canberra on Thursday.

Sydney residents are being asked to consider booking a staycation in the city for this year's Mardi Gras with hotel bookings currently down by 10 per cent as a result of COVID-19 and associated travel bans.

Tourism Accommodation Australia NSW CEO Michael Johnson said Mardi Gras was traditionally one of the busiest times of the year for CBD accommodation providers.

"Mardi Gras is an internationally recognised event which brings tens of thousands of people from around the world to Sydney," Mr Johnson said.

A Melbourne teenager diagnosed with coronavirus as her family was preparing to evacuate the Diamond Princess cruise ship, where four people have died, could recover and fly home before her quarantined family. 

Kaitlyn Soh, 16, was diagnosed when her family were preparing to evacuate the Diamond Princess in Japan and fly to Darwin, where they would have spent another two weeks in quarantine.

As she is a minor, her family were given the option of having just one parent stay back with her but they insisted on staying together in Japan.

If she ends up recovering before the family's 14-day quarantine period is over, her mother Aun Na Tan said Kaitlyn would fly home alone and stay with other relatives. 

Victorian chief health officer Brett Sutton told reporters at the Royal Childrens Hospital that authorities were working on the basis that a coronavirus pandemic was inevitable.

"I think it's much, much safer that way," Dr Sutton said. "We have to proceed with planning on the basis it is inevitable and we can and should expect more cases in Australia in the coming weeks or months. I don’t want to see us get caught out at all."

When asked about what contingency plans in Victorian hospitals, Dr Sutton said the plans had to be adaptable for any scenario and would be dependant on the severity of the outbreak.

"That might look like cohorting where you have a respiratory ward for coronavirus patients in hospitals," he said. "It might have a separate stream for emergency department patients."

Speaking at a press conference in Melbourne, Victoria Health Minister Jenny Mikakos has confirmed three incidents of racism towards staff at the Royal Childrens Hospital, condemning the "distressing" behaviour. 

"I am very concerned that there have been reports that some parents are refusing to have their children attended to by some of the staff at the hospital," she said. "That’s been done basis of fear of the coronavirus and ethnicity and it is completely unacceptable."

She stressed there were stringent protocols in place around the state in containing coronavirus and there was no risk to patients at any hospital in Victoria.

The economic impacts of the coronavirus outbreak are spreading.

Agricultural banking specialist Rabobank on Thursday said it expects demand for Australian beef from China to be well down through the first half of this year.

Australian beef producers lifted production through 2019 as the drought left many unable to keep up their herds.