A man has begun developing coronavirus symptoms 27 days after coming into contact with an infected person, causing authorities to fear for the worst.

A 70-year-old man in China's Hubei Province was infected with coronavirus but did not show symptoms until nearly four weeks later, the Chinese government revealed yesterday.

This could prove a devastating blow to the world if the virus's incubation period is longer than the presumed 14 days.

The Chinese government named the man simply as Jiang, and revealed in a statement that he came into contact with his sister, who had been infected, on January 24.

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But his symptoms appeared much later than expected.

Jiang developed a fever on February 20 and tested positive for coronavirus a day later, according to the government statement.

Australia's Department of Health recommends a self-isolation period of two weeks if one has been to China recently or come into contact with an infected person.

The department's advice has not changed, despite the development.

"The Australian Government's response to the novel coronavirus outbreak is evidence-based and proportionate," a Department of Health spokesperson told news.com.au.

"Australian authorities continue to monitor overseas developments closely.

"Our health emergency response arrangements are flexible and scalable, and are being tailored to most effectively respond to the evolving situation."

Seven rescued Australians who left the Diamond Princess, a cruise ship stranded because of a suspected coronavirus outbreak, have now tested positive for the disease.

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Three more are awaiting test results.

Globally, there have been more than 78,000 confirmed cases of coronavirus and 2363 deaths.