Medics are scrambling to evacuate two people from a luxury cruise ship stranded off the coast of Cape Verde, after a suspected outbreak of a rare respiratory virus killed three people, left three others seriously ill and forced nearly 150 people from across the world to isolate onboard.

The plight of the MV Hondius, which set off in March from southern Argentina carrying 149 people from 23 countries, emerged late on Sunday after the World Health Organization said it was investigating a suspected outbreak of hantavirus, a disease primarily found in rodents.

The UN health agency linked the rare disease to the deaths of three people, including a married couple from the Netherlands and a German national, and blamed it for making at least two others on the ship serious ill and sending a 69-year-old British tourist to intensive care in South Africa.

On Monday, a US travel blogger on the ship said the most difficult part was the question over what would come next for those onboard. “We’re not just headlines: we are people,” Jake Rosmarin said as he fought back tears in a video posted to social media. “People with families, with lives, with people waiting for us at home. There’s a lot of uncertainty, and that’s the hardest part.”

The cruise ship operator Oceanwide Expeditions said the first passenger, a Dutch national, had died on 11 April and that the cause of death had not been determined onboard. “On 24 April, this passenger was disembarked on St Helena, with his wife accompanying the repatriation,” it said in a statement.

Days later, the company said it had been informed that a woman, also a Dutch national, had become unwell and later died. Officials in South Africa said the woman, 69, collapsed at an airport in the country as she was trying to return to the Netherlands. She later died at a nearby hospital.

On 27 April, another person on the MV Hondius, a British national, became seriously ill and had to be evacuated to South Africa. He remains in intensive care in Johannesburg, where he is in critical but stable condition. “A variant of hantavirus has been identified in this patient,” the company said.

Another passenger, a German national, died on 2 May, of a cause “not yet … established”.

Two crew members, of British and Dutch nationality, had acute respiratory symptoms, one mild and one severe, and both required urgent medical care, the company said.

It noted that hantavirus infections, which are usually spread by infected rodents’ urine or faeces and can lead to severe respiratory illness and death, had not been confirmed in the two crew members. “Nor has it been established that the virus is connected to the three deaths associated with this voyage,” it said. “The exact cause and any possible connection are being investigated.”

Oceanwide Expeditions said almost 150 people of 23 nationalities had been onboard the ship. While it did not specify which cruise the passengers were on, the company’s website suggests it offers 33-night or 43-night “Atlantic Odyssey” cruises on the 107-metre-long (351ft) Hondius. Departing from Argentina, the tours travel through Antarctica and stop off at some of the world’s most remote islands.

The ship is currently anchored off the coast of Cape Verde, with passengers informed of what happened. “Strict precautionary measures are in process onboard, including isolation measures, hygiene protocols and medical monitoring,” said Oceanwide Expeditions.

The vessel had asked to dock at a port in Cape Verde but on Monday health authorities in the country said they would not authorise its docking “with the aim of protecting national public health”.

Instead they said they were in contact with authorities in the Netherlands and the UK about the Dutch-flagged ship. “This coordination has enabled a swift, safe and technically appropriate response, ensuring the clinical monitoring of patients and the preparation of all necessary precautionary measures, including a possible medical evacuation by air via air ambulance for patients under observation,” they added.

Oceanwide Expeditions said it was considering sailing to Spain’s Canary Islands, potentially Las Palmas or Tenerife, where further medical screening and handling could take place.

The company said it was working with Dutch authorities to organise the repatriation of the two crew members. “The body of the deceased individual is also planned to be included in this repatriation, along with a guest closely associated with the deceased,” it said, noting that the accompanying guest was “not symptomatic”.

It said the repatriation relied on several authorities working together. “This repatriation depends on many factors, including the authorisation and support of local Cape Verdean health authorities for the transfer of individuals requiring medical attention from MV Hondius.”

The Netherlands’ National Institute for Public Health and the Environment (RIVM), which is assisting with the situation, said the source of the infection remained unclear.

“You could imagine, for example, that rats on board the ship transmitted the virus,” a spokesperson told Reuters. “But another possibility is that during a stop somewhere in South America, people were infected, for instance via mice, and became ill that way. That all still needs to be investigated.”

On Monday, the WHO said the risk to the wider public remained low and that there was no need for panic or travel restrictions. “To date, one case of hantavirus infection has been laboratory confirmed, and there are five additional suspected cases,” it said in an earlier statement on Sunday.

South Africa’s National Institute for Communicable Diseases was carrying out contact tracing in and around Johannesburg in order to assess whether people had been exposed to the infected passengers.

The UK’s Foreign Office said it was closely monitoring reports of the suspected outbreak. “We are in touch with the cruise company and local authorities,” it said.

While it is rare, hantavirus infections can spread between people, according to the WHO. The family of viruses made headlines last year after the actor Gene Hackman’s wife, Betsy Arakawa, died following a hantavirus infection in New Mexico.

In 2019, a hantavirus outbreak in southern Argentina killed at least nine people. As officials raced to halt the spread of the disease, a judge ordered dozens of residents of a remote town to stay in their homes for 30 days, according to the Associated Press.