The first sign of COVID-19 began with a temperature, but 58-year-old Karen Honey put it down to a sore neck and stress.

Key points: Australians Karen and Jason Honey both became infected with coronavirus on the Diamond Princess cruise ship

Australians Karen and Jason Honey both became infected with coronavirus on the Diamond Princess cruise ship Ms Honey has suffered bouts of fever at night, regularly having to change her clothes and sheets

Ms Honey has suffered bouts of fever at night, regularly having to change her clothes and sheets Mr Honey has had no symptoms at all, despite testing positive for the virus

"I thought my headaches and temperature [were] from that more than anything else," she told 7.30.

It was early February and Ms Honey and her husband Jason, also 58, had spent 10 days mostly confined to their windowless cabin on the Diamond Princess docked in Yokohama, Japan.

The couple from Melbourne were in quarantine after an outbreak of the virus on the ship was publicly announced on February 1.

They posted a video to social media while quarantined in their room, saying: "We're stuck on this cruise ship, but we've got to go along with it and do the best we can."

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On February 11, Ms Honey was taken off the ship. A swab test had come back positive for COVID-19.

"That blew us both away. I thought I was clear," she said.

"I was feeling OK."

An ambulance took Ms Honey 120 kilometres from the ship to a hospital in Isesaki.

Mr Honey remained onboard, wandering the lonely corridors and whiling his time away with work. He took an occasional escape to the upper deck for a sneaky smoke.

In hospital, Ms Honey suffered bouts of fever, sweating through the night. The bed sheets were regularly soaked.

A few days later on Valentine's Day, she said she felt much better.

"[That] was the first night that I didn't wake up where I've had to change my clothes and the bedding because I sweated so much," Ms Honey said.

"My temperature during the day [was] fine."

Then Jason Honey tested positive

Jason Honey was left on board the Diamond Princess after Karen Honey was sent to hospital. ( Reuters: Kim Kyung-hoon )

At the time, Mr Honey remained optimistic. Asked if he thought he would catch the virus after sharing the same cabin with Ms Honey, he said: "I'm as fit as a Mallee bull. I'll be fine."

But by February 20, Mr Honey tested positive too. It was inevitable after such close contact with his wife.

He had coronavirus without even realising.

"It's really weird," he said.

"I've got no symptoms."

Now, Mr Honey is in hospital. He's been there for 10 days. His wife has been there for more than three weeks.

"I feel fine. I've had no fevers, no coughs, no nasal problems, no aches, no pains. Nothing," he said.

It is no surprise to professor of global biosecurity at the University of New South Wales Raina MacIntyre who said asymptomatic transmission was making COVID-19 hard to control.

"This is the major difference with SARS," she said.

"SARS was only infectious when people had symptoms, so you could identify someone who was infectious because they had symptoms."

Professor MacIntyre said asymptomatic cases could be responsible for "undetected chains of transmission in the US".

According to the World Health Organisation, COVID-19 symptoms are similar to the flu, including fever, tiredness and a dry cough.

Other signs are aches and pains, a runny nose, sore throat or diarrhea.

Some people will have symptoms, others will not and 80 per cent will recover without needing special treatment.

'Nothing the doctors can do'

Ms Honey's symptoms eventually disappeared and she returned a negative result, but she recently tested positive again.

That is consistent with reports from China and Japan of patients being discharged and then testing positive for the second time.

This could mean the virus is biphasic, where the virus lurks around undetected before recurring.

With no cure and no vaccine, the Honeys can only wait until their bodies defeat the virus.

"It's just got to run its course," Mr Honey said.

"You've just got to build your immunity to it. There's nothing the doctors can do."

Since arriving in hospital, the couple has been isolated in separate rooms, but recently they were allowed to visit each other.

In all, they have now spent more than four weeks in quarantine both on the ship and in hospital and there is no end in sight.

"Karen's had a gutful and I've had a gutful too," Mr Honey said.

"Today was not a good day mentally. It was a real struggle for Karen and for me too, for that matter.

"We very much feel like the forgotten Australians here in Japan."