Western Australia's Chief Health Officer Dr Andrew Robertson on Sunday confirmed the 78-year-old died at Perth's Sir Charles Gairdner Hospital in the early hours of Sunday morning.

The man's wife said in a statement that her husband passed away peacefully knowing his family loved him. She was also diagnosed with the virus a few days ago and is in a stable condition in the same hospital.

It's not known if the man's wife got the virus from her husband, but both were on the Diamond Princess cruise ship, Dr Robertson said.

The man was diagnosed with COVID-19 about 10 days ago while in isolation at Howard Springs in the Northern Territory after being quarantined aboard the Diamond Princess and then flown out of Japan.

"He was in his late 70s, like many people in that age, they're more likely to have other chronic conditions and it would obviously make being able to fight off this virus more difficult," Dr Robertson told reporters in Perth.

He added that the elderly man's death didn't come as a surprise to doctors as it's known COVID-19 can start off relatively mild before it progresses.

"It's often the second week where people will deteriorate and get significant viral pneumonia," Dr Robertson said, insisting there was no community risk as the man had been in isolation ever since he was diagnosed.

Premier Mark McGowan said he has been asked not to disclose the man's identity, and told WA residents not to panic.

"All West Australians should continue doing what we ordinarily do," he said.

"Go to work, attend functions and events engage with family and friends. Don't change what you're currently doing and whatever you do, don't panic in this situation."

Reiterating health advice to use hand sanitisers and asking people not to walk the streets with face masks on, Mr McGowan urged WA to get flu vaccines ahead of this year's season.

He also assured West Australians that hospitals were gearing up in case the situation worsened.

Prime Minister Scott Morrison said he was "very saddened" to hear about the death of the elderly Perth man.

"We join his family and friends in mourning his passing ... We will continue to do all we can to protect Australians from #coronavirus," he said in a tweet on Sunday.

Federal Health Minister Greg Hunt said the Morrison government had a national COVID-19 plan with health authorities across the country meeting daily to monitor the situation.

"With the international spread of this virus, it is almost inevitable that we will see more cases of COVID-19 in Australia in coming weeks," he said in a statement on Sunday.

It comes as the government defends its decision to ban foreign visitors entering Australia from Iran to prevent the spread of the coronavirus, rather than South Korea which has a much higher level of cases.

Home Affairs Minister Peter Dutton on Sunday said that of the 106 deaths that have been reported outside of China, 43 have been in Iran.

The new travel restrictions came in as four people returning from Iran were confirmed as having contracted the virus.

NSW health authorities confirmed the state's fifth and six cases as a man in his 40s and a woman in her 50s who both returned to Sydney from Iran.

The two cases are not connected, and they arrived on different days.

New cases in Victoria and Queensland also came from Iran: a Victorian woman who was confirmed as testing positive on Sunday, and a 63-year-old Gold Coast beautician who arrived on Monday.

Australian Associated Press