Three people have died after a suspected hantavirus outbreak on a cruise ship sailing in the Atlantic.

One case of hantavirus infection had been confirmed and there were five additional suspected cases, the World Health Organization told Agence France-Presse on Sunday.

Of the six people affected, three died and one is in intensive care in South Africa, the WHO added. Two of those who died were a husband and wife aged 70 and 69.

The person in intensive care is a 69-year-old British national, according to the BBC.

The outbreak was reported on the MV Hondius, which was travelling between Argentina and Cape Verde.

The ship is operated by the Dutch tour company Oceanwide Expeditions. The company has not responded to a request for comment.

Earlier on Sunday, South Africa’s health ministry told AFP there had been an outbreak of a “severe acute respiratory illness”, which had killed at least two people, with a third in intensive care in Johannesburg.

The patient treated in Johannesburg tested positive for hantavirus, a family of viruses that can cause haemorrhagic fever, South African spokesperson Foster Mohale said.

Hantavirus is usually caught through contact with urine or faeces from infected rodents, but in rare cases can spread between people. It can lead to severe respiratory illness.

The first person to develop symptoms was a 70-year-old passenger. He died onboard the ship and his body was currently on the island of Saint Helena, a British overseas territory in the South Atlantic, Mohale said.

The man’s 69-year-old wife also fell ill onboard and was evacuated to South Africa, where she died in a Johannesburg hospital.

Their nationalities had not yet been established but a source close to the case, speaking on condition of anonymity, said a Dutch couple were among the dead.

The third fatality was still onboard the ship on Sunday evening.

Another passenger, a 69-year-old Briton, was also evacuated to Johannesburg, where he was being treated in intensive care.

Discussions were under way to decide whether two other sick passengers should be placed in isolation in hospital in Cape Verde, an archipelago off the west coast of Africa, after which the ship would continue to Spain’s Canary Islands, the anonymous source said.

The WHO said it was “facilitating coordination” between national authorities and the ship’s operators to organise the medical evacuation of two passengers with symptoms.

The MV Hondius is listed as a polar cruise ship on the websites of several travel agencies. One of the cruises offers an itinerary departing from Ushuaia in Argentina and sailing to Cape Verde, with stops in the islands of South Georgia and Saint Helena.

The vessel can accommodate about 170 passengers and has 70 crew members. According to several online ship-tracking sites, the MV Hondius was just off the port of Praia, the capital of Cape Verde, on Sunday.

The UK’s Foreign Office said: “We are closely monitoring reports of a potential hantavirus outbreak on the cruise ship Hondius and stand ready to support British nationals if needed. We are in touch with the cruise company and local authorities.”