It’s the nightmare scenario – and one that all cruise ship companies and their passengers dread and hope will never happen.

But, on occasions, it does and the results can be devastating, as those on board MV Hondius, stranded in the Atlantic ocean off the coast of the Cape Verde islands, are discovering.

Three passengers have died and two crew members are seriously ill following a suspected outbreak of hantavirus, which, according to the US Centers for Disease Control, kills some 40 per cent of those who contract it.

Hantaviruses are spread by rodents, through contact with their urine, droppings and saliva, with symptoms ranging from a mild flu-like illness to major respiratory issues or internal bleeding.

Being unwell next to anyone in close confines will be a source of great anxiety for the passengers and crew.

The MV Hondius is a small expedition ship – offering little opportunity to keep away from other passengers who might be ill.

Operated by Oceanwide Expeditions, a Dutch company that specialises in cruises to Antarctica and the Arctic, there are currently 149 passengers on board – 19 of them British, more than from any other country, plus a crew of 57 and 13 expert guides.

But in some respects, if you fall ill on a cruise ship you may get better – and faster – care than if you were on land trying to see a GP.

Under rules drawn up by the American College of Emergency Physicians, in conjunction with the cruise industry trade body, Cruise Lines International Association, CLIA, all ocean-going cruise ships worldwide must have medical staff on call at all times – and they must be trained in emergency medicine. 

But MV Honduis is not a member of CLIA.

The bigger the ship, the more extensive the medical facilities. On most cruise ships, minor surgery or procedures that do not require general anaesthetic can be performed – from stitches and draining abscesses, to removing cysts and benign growths.

Even if you fall ill with a mystery illness, many ships will have the equipment necessary to run tests to determine what might be wrong.

Ships have a laboratory set-up for testing blood samples, including a full blood count as well and may have other facilities to help diagnose a range of conditions, including liver disease, kidney problems, cardiac issues and metabolic disorders such as diabetes and gout.

I have been on cruise ships that have as many as six hospital-style beds, but it is unlikely that MV Hondius has this many.

We know that the cruise ship only has one doctor on board, most likely assisted by two nurses. Coping with an emergency such as this will stretch the ship’s medical operations to the limit.

Two members of the crew – one of whom is British, the other Dutch – are suffering acute respiratory symptoms, one mild, the other severe. Both require urgent medical care and are waiting to be taken off the ship.

Viruses and bugs of all kinds spread fast on cruise ships because of the large number of people sharing confined spaces. Add in the fact that many people on cruise ships tend to be older and have less robust immune systems, and you can see how in the wrong circumstances it can become a disaster.

There are safeguards, of course. All ships insist on sanitising hands before meals and before congregating at events and onboard entertainment.

In this case, in an attempt to stop the virus from spreading, all passengers will be told to remain in their cabins and contact with crew will be minimal. ‘Strict precautionary measures are in process on board, including isolation measures, hygiene protocols and medical monitoring,’ said Oceanwide Expeditions.

Lessons will have been learned from the famous case in 2020, when the Diamond Princess, part of the Princess Cruises fleet, experienced a horrific outbreak of coronavirus during a 29-night voyage from Singapore to Japan via Vietnam, Hong Kong and Taiwan.

The ship was carrying 2,589 passengers and 1,041 crew, including 77 Britons, when it set sail in January, but a month later, the World Health Organisation announced that the Diamond Princess had more cases of Covid 19 than anywhere outside China.

In total, the ship would confirm 712 cases and 14 deaths – and it became referred to as the ‘corona plague ship’.

Deaths on board are rare, but clearly distressing. Cruise lines inform their crew about a death with a special coded announcement. One company uses ‘Operation Bright Star’ for a medical emergency and ‘Operation Rising Star’ to indicate that a passenger has died. 

On Ambassador Cruises, a British company that sails from Tilbury Docks in Essex, ‘Alpha’ is used when someone has passed away.

It is estimated that around 200 people die each year on a cruise – mainly from strokes, heart attacks or trauma from a fall.

All ships have a morgue, usually big enough to store up to five bodies, but on MV Hondius it will be considerably smaller.

The first death on the ship was on 11 April, but the man’s body was not brought ashore for a further 23 days, when it was finally taken off on the island of St Helena. 

The man’s wife disembarked at the same time – but three days later she, too, died.

On May 2, a third passenger, who was German, died, and this person is currently in the ship’s morgue, a spokesperson confirmed to the Daily Mail.

‘I do not know how big the morgue is on the ship,’ she said. ‘This is a very difficult situation but we are handling it as well as possible. We do not expect to have a conclusive outcome in terms of coming into port until tomorrow.’

In the past, there have been stories of on board morgues filling up and bodies having to be put in wine cellars. But this is rare.

Bodies are normally either taken off ships at the next port of call – which is expensive – as the body then has to be flown home – or remain on board until reaching their home port.

It is still possible – although rare and requires a great deal of paper work – to be buried at sea, amounting to a substantial financial savings for relatives of the deceased.

Ceremonies in these circumstances are held early in the morning before other passengers are up and about. 

The ship would slow to its lowest speed and senior officers form a guard of honour, as the body, wrapped in a biodegradable bag, is placed on a hydraulic platform and tipped into the sea at the appropriate moment.

A CLIA spokesperson said: ‘We are aware of reports regarding cases of Hantavirus associated with a recent voyage on a non-member cruise line. Our thoughts are with those affected. CLIA-member cruise lines are required to adhere to comprehensive health, safety, and medical policies designed to detect, prevent and mitigate illness.’