The first suspected 'generation-three' hantavirus case has emerged, potentially signifying the first stage of a much wider outbreak of the deadly rat-borne disease.

An Italian man has been transferred to hospital after boarding a Dutch KLM flight alongside a woman who later died from a hantavirus infection.

So far, no cases have been confirmed in people who were not on board the MV Hondius, so there is no evidence that the virus has spread beyond the confines of the ship. 

However, if the 25-year-old from the southern region of Calabria tests positive, it will prove the disease is a lot more contagious - and far less contained - than previously thought.

The man, alongside three other Italians, had been placed in quarantine after boarding the flight from Johannesburg to Amsterdam on April 25.

Authorities were concerned that they may have been infected by the presence of Miriam Schilperoord, a 69-year-old passenger of the cruise who was ultimately asked to leave the flight because she was so ill.

On April 26, she died upon arrival at the emergency department of Johannesburg hospital from hantavirus, 15 days after the death of her husband, 70-year-old Leo Schilperoord, also known as 'patient zero'.

It comes as French health minister Stephanie Rist admitted there are still things we don't know about the killer virus, including whether it has mutated. 

World Health Organisation (WHO) chief Tedros Adhanom Ghebreyesus has warned that 'given the long incubation period of the virus, it's possible we might see more cases in the coming weeks'.

'There is no sign that we are seeing the start of a larger outbreak,' Ghebreyesus told a joint news conference in Madrid with Spanish Prime Minister Pedro Sanchez.

'But of course the situation could change,' he added, cautioning that the world can expect to see more cases due to the level of interaction among passengers before the infection was confirmed.

The Italian man follows the discovery of another contact case in Brittany, northwestern France, on Tuesday morning.

There, a person who may have contracted the virus from a cruise passenger has been sent to the University Hospital of Rennes for further checks.

'For now, this remains only a contact case, a person who has been in contact with someone carrying the virus. So there is no need to panic, we are only talking about a single case which has been contained,' said Quentin Le Gaillard, mayor of the Breton port city.

Twelve Dutch medical staff have also been quarantined for six weeks, after workers in a hospital in Nijmegen did not follow strict protocols while handling a hantavirus patient's blood and urine samples. 

Bertine Lahuis, the chair of the Radboudumc hospital's executive board, said: 'We will carefully investigate the course of events to learn from this so that it can be prevented in the future.'

The hospital added that the infection risk is very low and patient care continues uninterrupted, after it admitted a Hondius passenger infected with hantavirus on May 7.

While no one has tested positive who wasn't already on the ship, the long incubation period of the virus means that it is impossible to know whether passengers who disembarked early on April 24 have passed on the disease.

According to Dr Steven Quay, all generation-two cases – those involving people who developed symptoms after contact with 'patient zero' – took an average of 22 days to become sick.

That means generation-three cases – involving anyone who contracts the infection from the passengers – should start showing up around May 19, if the same incubation period of approximately three weeks remains true, he said.

So far, three people - Dutch national Mr Schilperoord, his wife Miriam, and a German woman - have died after travelling on the Hondius, two of whom were confirmed to have contracted the virus.

In previous outbreaks of the Andes strain of hantavirus in Argentina - the strain that is transmissible between humans - the peak time for symptom onset was 22 to 28 days. 

'We now have 10 hantavirus cases, one apparent patient zero and nine human-to-human generation two cases,' Dr Quay said.

'May 19 is a good date to watch for... If cases continue beyond that point they will probably be generation-two to generation-three cases.'

Before the outbreak was identified, some 29 cruise passengers disembarked from the Hondius on Saint Helena on April 24 - the destination marking the end of the first leg of the trip.

Those who disembarked included Mrs Schilperoord, as well as a Swiss national now in hospital in Zurich who tested positive for hantavirus.

The Dutch woman went on to board an Airlink flight to Johannesburg on April 25, carrying 82 passengers and six crew members.

But by that point, she was severely ill. 

She then briefly boarded a second flight to Amsterdam, before being asked to exit the plane before takeoff.  

Health authorities are rushing to identify any potential contact cases who may have contracted the virus on the two flights.

A British national who disembarked from the MV Hondius at the British Overseas Territory of Tristan da Cunha, in the South Atlantic, is also suspected of having the disease.

The passengers left the vessel before it had become clear they may be carriers of the lethal virus, and may have come into contact with hundreds of people over the past two weeks.

While hantaviruses are usually spread by wild rodents, it is now all but proven that the disease can be passed from person to person via bodily fluids, which can harbour infectious particles.

Symptoms can include shortness of breath, fever, extreme fatigue, muscle aches, stomach pain, vomiting, and diarrhoea.

Experts have insisted that there is little risk to the public and that this isn't another pandemic, because the virus spreads only through close contact, such as kissing or sharing food or drinks. 

Ghebreyesus said: 'This is not another Covid. And the risk to the public is low. So they shouldn't be scared, and they shouldn't panic.' 

Passengers of the Hondius have been sent a questionnaire asking whether they kissed or hugged anyone who was ill or died, or were within 6ft of an infected person for at least an hour cumulatively. 

Other questions included whether they shared sexual contact, touched soiled bedding or clothing, shared a bed, slept in the same room, shared a bathroom, shared a toothbrush, cigarette or vape, or came into contact with bodily fluids.

But there are concerning signs that the Andes strain of the virus may be even more contagious than previously known. 

Professor Joseph Allen, of Harvard University, raised alarm when he revealed that a doctor onboard the Hondius told him that the 'messaging' about close contact transmission had been misguided.

The doctor told him that some of those infected had not had close contact with patient zero, and had only crossed paths with him in dining rooms or lecture areas.   

If the doctor is right, and physical contact isn't required to become infected, this could suggest the Andes strain is spread through airborne transmission.

In a previous outbreak of the strain in Chubut Province, Argentina, it was reported that someone became sick with the virus only after saying 'hello' in passing to an infected person at a birthday party. 

Despite people sitting at different tables, up to 6ft apart, several others were infected at the same gathering.

And during the same outbreak, two patients who had been admitted to hospital for other ailments contracted hantavirus by being placed in the same rooms with infected people - despite no close contact. 

A French national, a man from the US, and a Spaniard have all tested positive for the virus since being evacuated from the ship over the weekend.

If all the patients contracted the disease from patient zero, then the reproduction rate – the number of people each person infects – is nine. 

Such a rate is as high as the Covid-19 Omicron variant, although the fact that passengers were confined together in the ship will have driven it much higher than would be expected out in the wider world.

Two British citizens were among the 29 passengers who left the ship early at Saint Helena and travelled back home.

They are now self-isolating in the UK, and while neither have symptoms, they will have crossed paths with others on their journey.

It comes as some 20 Britons, one German who lives in the UK, and one Japanese national are due to remain at Arrowe Park Hospital in Merseyside for 72 hours after being evacuated from the ship.

There, they will be monitored by doctors and then told whether they can isolate for up to 45 days at home or at another location, in what medics described as 'a planned, controlled and carefully managed arrangement'.

The Arrowe Park site, close to the village of Upton, was used to house British citizens returning from Wuhan, China, at the start of the Covid-19 pandemic six years ago.

If May 19 passes by without the emergence of 'generation-three' infections, the next date to focus on will be June 21 - when the incubation period will have run its course.

By that point, there will be no chance that anyone else could be infected from the first outbreak.

More than 120 passengers and crew on the MV Hondius were flown out from Spain's Canary Islands on Sunday and Monday, and countries have adopted different health measures for their returning evacuees.

Most countries have followed the WHO's guidelines, which include a 42-day quarantine and constant monitoring of high-risk contacts.

But in the United States, Jay Bhattacharya, acting director of the Centers for Disease Control and Prevention (CDC), said American passengers would not necessarily be quarantined.

'I hope they (countries) will follow the advice and recommendations we are making,' Ghebreyesus said in Madrid.

The Hondius presented diplomatic challenges as different countries negotiated over who would receive it and treat its passengers.

Cape Verde refused to receive the ship, which remained anchored offshore the capital Praia as three people were evacuated to Europe by air last week.

Spain allowed the vessel to anchor off the Canary Islands for the evacuation of passengers and crew on Sunday and Monday, but the Atlantic archipelago's regional government fiercely opposed the measure.

Defending his government's policy, Sanchez said the 'world does not need more selfishness or more fear. What it needs are countries that show solidarity and want to step forward'.

Eighteen passengers from the cruise ship have been repatriated to the US and are being monitored at specialist medical units. 

Sixteen of those people, including one who tested positive, are at the University of Nebraska Medical Centre, and two others are in Atlanta. 

All in Nebraska are asymptomatic, while one person in Atlanta is experiencing symptoms, according to health officials.

The positive case was sent to the Nebraska Biocontainment Unit upon arrival, while other passengers went to the National Quarantine Unit for assessment and monitoring.

Following the positive test result of a French female national, it has been revealed that cruise ship doctors dismissed her symptoms as mere signs of 'anxiety' before she became critically ill.

The woman, who was evacuated from the Hondius in Tenerife over the weekend, is now in a 'very critical' condition and is deteriorating rapidly in hospital.

According to Spanish health minister Javier Padilla, she was deemed symptomless despite suffering with a cough and the flu.

And despite the deaths of three people who had been onboard the ship, doctors from the European Centre for Disease Prevention and Control (ECDC) and the Spanish foreign health service dismissed her symptoms as just manifestations of stress.

'They were not thinking that these symptoms were compatible with hantavirus. Why? Because what she was telling [them] was [that she had] an episode of coughing some days ago that had disappeared, and what she was having at that moment was kind of like stress or anxiety or nervousness. So it was not catalogued [as hantavirus],' Padilla said. 

The four other French citizens repatriated from the cruise ship have been 'immediately placed in strict isolation until further notice', French Prime Minister Sébastien Lecornu said. 

The French ministry of health has also identified 22 possible contact cases.

The woman is the third evacuee from the hantavirus-hit cruise ship who has been confirmed to have the deadly disease after being repatriated.

A Spaniard, who is one of 14 quarantining in a military hospital in Madrid after being evacuated from the ship, provisionally tested positive for the illness on Monday, despite showing no symptoms.

He has developed a fever and breathing difficulties, the health ministry said on Tuesday, adding that the patient is stable and has shown no evident clinical deterioration. 

After all passengers disembarked from the vessel, it set sail for the Netherlands late on Monday evening, with 25 crew as well as a doctor and a nurse, and is expected to arrive on May 17.

Those remaining onboard include 17 people from the Philippines, four from the Netherlands (including the two medical staff), four from Ukraine, one from Russia and one from Poland. 

WHO has only officially confirmed seven cases of the Andes hantavirus among people who were passengers on board the cruise ship.

Despite reports from the US Department of Health and Human Services on Sunday that one of the 18 repatriated Americans tested mildly positive for the lethal Andes strain of hantavirus, the WHO and the Spanish government disregarded these findings.

The Spanish health ministry said that the US citizen's tests in Cape Verde gave a result considered by the Americans as a 'weak positive', 'although for us it was not conclusive', and another that was negative, the ministry said. 

'The person in question did not show symptoms when they were in Cape Verde. However, the US authorities have decided to treat the case as positive. For that reason, they requested a separate evacuation, which was carried out in a separate boat,' the ministry added.

This brings the number of officially confirmed cases to seven, including Mrs Schilperoord and a German woman who died, a Briton hospitalised in South Africa, a Briton hospitalised in the Netherlands, a Dutch man also in the Netherlands, a Swiss national and a French national.

WHO has listed two other ‌highly suspected cases - Mr Schilperoord, who died before being tested, and a British national on Tristan da Cunha, a remote island where there were no tests available. 

Another British national who was previously hospitalised with hantavirus in South Africa after falling sick on the cruise is 'clinically improving but still ill', a health ministry spokesperson said. 

The third British man with a confirmed case is 56-year-old Martin Anstee, a former police officer, who is receiving treatment in the Netherlands after working on the cruise ship.