David and Sally Abel have posted regular updates on Facebook and YouTube pleading with the UK Government to be flown home from the Diamond Princess, which is quarantined near Yokohama, Japan.
Yesterday afternoon, Mr Abel said the couple were well and had passed all medical checks run by the ship, which has 74 Britons on board.
But this morning, UK time, Mr Abel posted on Facebook: "There is going to be a time of quiet.
"We have been proved positive and leaving for hospital soon. Blessings all xxx."
In a follow-up post, he said: "Frankly I think this is a setup! We are NOT being taken to a hospital but a hostel. That's where partners are sent waiting out there (sic) quarantine.
"No phone, no wi-fi and no medical facilities. I really am smelling a very big rat here! Waiting for the transfer now. xx"
People with coronavirus illness - also known as Covid-19 - are being taken off the ship for treatment at hospitals in Japan.
According to the latest Government figures, a confirmed diagnosis for Mr and Mrs Abel would put the total number of Britons from the ship with coronavirus at six.
It comes as the Foreign and Commonwealth Office (FCO) said it was "working to organise" a flight back to the UK for British nationals on the Diamond Princess.
Pressure has been mounting on the Government to evacuate Britons in light of the cramped conditions on board, and the fact that the number diagnosed with the virus on the ship keeps rising.
On Sunday, the US chartered two planes and repatriated around 340 of its citizens from the vessel, while other countries are also flying their citizens home.
A statement from the Foreign Office said: "Given the conditions on board, we are working to organise a flight back to the UK for British nationals on the Diamond Princess as soon as possible.
"Our staff are contacting British nationals on board to make the necessary arrangements. We urge all those who have not yet responded to get in touch immediately."
On Monday, the Japanese Health Ministry confirmed 99 more people on the Diamond Princess had been diagnosed with the illness, bringing the total to 454.
The data comes after Sir Richard Branson said Virgin Atlantic was "in discussions" with the Government over whether he could help those stranded.
He responded following an appeal from Mr and Mrs Abel, who have asked the British businessman and philanthropist to charter a special plane.
On Monday, the couple's son Steve Abel renewed appeals for the Government to help his parents, saying he feared they may become separated in Japan.
Princess Cruises president Jan Swartz said the firm has worked with authorities to send more doctors and nurses on board the ship and has helped fulfil 2,000 prescription requests.
However, there is still uncertainty over whether other passengers will be able to leave the ship at the end of the 14-day quarantine period on Wednesday.
Meanwhile, the Government has block-booked the Holiday Inn Heathrow Ariel hotel as a potential quarantine zone for people arriving in the UK who develop coronavirus, or for Britons evacuated from overseas.
As of Monday afternoon, 4,501 people in total have been tested for Covid-19 in the UK, of which nine have come back positive.
The death toll in mainland China rose by 98 to 1,868, in figures announced early on Tuesday morning, while the number of people infected globally stands at 72,436, according to the country's National Health Commission.
Late on Monday, Public Health England (PHE) published guidance to schools telling them there is no need for children to stay off if staff, pupils or family members are undergoing Covid-19 testing.
Only if a case is confirmed will PHE local health protection teams take action, advising the school and tracing close contacts of those affected.
However, if a child or staff member feels ill and believes they have been directly exposed to Covid-19, the school is told to call NHS 111, or 999 in an emergency.
In this instance, schools should "try to find somewhere safe for the unwell person to sit which is at least two metres away from other people", the guidance says.
"If possible, find a room or area where they can be isolated behind a shut door, such as a staff office or meeting room. If it is possible to open a window, do so for ventilation.
"They should avoid touching people, surfaces and objects and be advised to cover their mouth and nose with a disposable tissue when they cough or sneeze and put the tissue in the bin.
"The room will need to be cleaned once they leave."
The guidance says a separate bathroom should be used if one is available.