Authorities around the world are racing to trace dozens of passengers who disembarked from the cruise ship at the centre of a deadly hantavirus outbreak before isolation measures were implemented.

It emerged for the first time on Thursday that at least 29 passengers of 12 nationalities left the MV Hondius on 24 April after the first fatality, prompting a scramble to identify and track their movements since then.

The disclosure came as the World Health Organization said that five of the eight suspected cases linked to the ship had been confirmed and that other cases may be identified.

“Given the incubation period of the Andes virus, which can be up to six weeks, it’s possible that more cases may be reported,” the organisation’s director-general, Tedros Adhanom Ghebreyesus, told a news conference. “While this is a serious incident, WHO assesses the public health risk low.”

The Dutch health ministry said a woman who had not been on the ship was being tested for hantavirus and being kept in an isolated ward in an Amsterdam hospital after showing symptoms. A positive test could make her the first known person not on the MV Hondius to become infected in the outbreak.

Oceanwide Expeditions, the Dutch cruise company that operates the vessel, said 29 people – and the body of the first fatality – had disembarked at the British territory of Saint Helena on 24 April. It added that the first confirmed case of hantavirus was not reported until 4 May. The disembarked passengers – including six US and seven British citizens – had been contacted, the company said. Most, if not all, are believed to have returned home.

“The Australian went back to Australia, the one from Taiwan to Taiwan, the Americans to all corners of north America. The Englishman to England, the Dutch to their homes,” a Spanish passenger, who remains on board the Hondius, told El País.

A man who made his way to Switzerland was being treated at a Zurich hospital after testing positive for the virus. Swiss authorities said there was no risk to the public. In the US, the Centers for Disease Control and Prevention (CDC) was monitoring passengers who had travelled to Georgia, California and Arizona, the New York Times reported. None had shown sign of illness.

Two passengers who are self-isolating at home after returning to Britain were showing no symptoms, according to the UK Health Security Agency (UKHSA). Prof Robin May, the agency’s chief scientific officer, suggested the pair and other passengers who returned would be asked to self-isolate for 45 days. “For the broader public, not directly involved in this cruise ship, the risk here is really negligible,” said May.

Two Singapore residents who had been on the Hondius had been isolated and are being tested, Singapore officials said. A Danish citizen who had been on the cruise was in self-quarantine and showing no symptoms, the Danish Patient Safety Authority said.

The outbreak has killed three people and caused global alarm. Hantaviruses are a group of viruses primarily found in rodents but which can infect humans and cause flu-like symptoms, pulmonary syndrome and respiratory failure.

The Andes hantavirus can spread among humans through very close contact, but is less contagious than Covid. There are no vaccines.

Three people with symptoms who were medically evacuated – a 41-year-old doctor, a 65-year-old German passenger and Martin Anstee, 56, a British expedition guide – are being treated in the Netherlands.

The effort to trace disembarked passengers came as the Hondius, with 149 people left onboard, departed waters around Cape Verde, where it was denied permission to dock, and headed for Tenerife, in Spain’s Canary islands, where it was expected at around midday on Sunday.

The president of the archipelago, Fernando Clavijo, voiced concerns over the central government’s decision to allow the ship into the Canaries, and requested a meeting with the Spanish prime minister, Pedro Sánchez.

Spain’s health minister, Mónica García, met Clavijo on Thursday and said there was no threat to public health. The Hondius would remain at anchor and not dock in port, she said.

“Its stay in Canary island waters will be the minimum necessary from a health and logistical point of view, as planned from the beginning and as established by the protocols. Passengers will be evaluated onboard the ship and will only disembark for transfer or repatriation with protective equipment, with a specific health worker, and without coming into contact with the population.”

EU nations are expected to begin evacuating their citizens from the Canaries from Monday 11 May. The 14 Spanish nationals onboard the ship – including one crew member – are to be transferred from Tenerife to the Gómez Ulla military hospital in south-west Madrid.

Spain’s opposition conservative People’s party (PP) accused the socialist-led government of mixed messaging over quarantine procedures after the defence ministry said it would be voluntary, while García said there were legal tools to make it mandatory.

The Polar vessel sailed on 1 April from Ushuaia, a city in southern Argentina known as the “end of the world”, and made stops in Antarctica and several remote Atlantic islands.

A 70-year-old Dutch man showed symptoms on 6 April and died five days later but it was attributed to natural causes and raised no alarm. His body was taken off the ship on 24 April when it docked at Saint Helena, where other passengers disembarked.

His 69-year-old Dutch wife flew to South Africa and in Johannesburg briefly transferred to a KLM flight before being taken off for treatment. She died. A KLM stewardess who was in contact with her is in an isolation ward at an Amsterdam hospital after showing possible symptoms of infection, the Dutch broadcaster RTL reported.

Contact tracing was under way for people who had shared the dead woman’s flight from Saint Helena, the World Health Organization said.

The body of a German passenger who developed a fever on 28 April, and died on 2 May, remains on the ship.

One theory has linked the outbreak to a birdwatching expedition in Argentina by the Dutch couple before they boarded the Hondius. Argentina has Latin America’s highest incidence of hantavirus and has reported 101 infections since June 2025, roughly double to the year prior. Argentina’s health ministry said it would carry out rodent trapping and analysis in Ushuaia, the cruise’s point of origin.