Why MV Hondius hantavirus outbreak raises fears of Andes strain spreading beyond close contact

Health agencies are tracing passengers and contacts linked to the MV Hondius hantavirus outbreak. The spread of Andes virus beyond the ship has sharpened questions about how it may transmit.

In Short

• A British contact on Tristan da Cunha tested positive off the ship
• A KLM crew member was hospitalised but later tested negative
• Early illnesses resembled respiratory infection before tests confirmed the Andes strain

Global health authorities are racing to contain a widening hantavirus outbreak linked to the Dutch expedition cruise ship MV Hondius, amid growing concern that the Andes strain involved may not always spread only through prolonged close contact.

While experts continue to stress that sustained human-to-human transmission remains rare, recent cases connected to the outbreak have highlighted lingering uncertainties around the virus and raised fears that some infections may occur outside traditionally recognised high-risk exposure settings.

The latest updates from the World Health Organization (WHO), alongside reports from national health agencies from several countries, show that confirmed and suspected cases are now spread across several countries after passengers and contacts disembarked from the ship following its South Atlantic voyage.

At least three people have died, while confirmed infections continue to emerge among evacuated passengers.

The outbreak has drawn international attention because the Andes virus – unlike most hantaviruses – is known to spread between humans in rare circumstances. Scientists and public health experts say the exact mechanism of transmission is still not fully understood, even decades after the strain was first identified in South America.

“There is still a lot we don’t understand about the virus even though it has been around for decades,” Dr Soumya Swaminathan, former chief scientist at the World Health Organisation (WHO) told India Today in an interview.

BEYOND CLOSE CONTACT

One development that has particularly drawn attention is the confirmation that a British national who was not on board the MV Hondius has tested positive after exposure linked to the wider transmission chain.

According to health authorities cited by the BBC and other international reports, the Briton is believed to have contracted the virus on Tristan da Cunha after contact with an infected traveller connected to the ship’s route.

Officials have not suggested widespread casual transmission, but the case has added to concerns that the virus may occasionally spread in situations beyond the prolonged, intimate contact usually associated with Andes virus infections.

At the same time, authorities have sought to reassure the public over possible spread during air travel.

A KLM flight attendant who had contact with a Dutch passenger later found to be infected was hospitalised in Amsterdam after developing symptoms initially considered compatible with hantavirus.

However, the WHO later confirmed that the crew member tested negative.

Dutch health officials had monitored dozens of passengers and airline personnel after the infected traveller flew from Saint Helena to Johannesburg and onward to Amsterdam.

Several individuals seated near the infected passenger were categorised as higher-risk contacts, though no confirmed onboard transmission during the flight has been established so far.

DEADLY ANDES STRAIN

The outbreak began during a polar expedition voyage that departed from Ushuaia, Argentina, in April. Early cases were initially mistaken for common respiratory illness before laboratory testing identified the Andes strain of hantavirus. Three deaths have since been linked to the outbreak, including a Dutch couple and a German passenger.

Passengers were eventually evacuated in Tenerife in the Canary Islands under strict biosecurity measures. Several countries, including France, the United States and Britain, launched large-scale contact tracing operations for exposed travellers.

French authorities said one evacuated passenger remains in intensive care, while WHO chief Tedros Adhanom Ghebreyesus warned countries to prepare for additional cases because of the virus’s incubation period and the extensive international travel undertaken before the outbreak was fully recognised.

Reuters reported that French officials are also investigating whether the virus may have undergone any mutations, although early sequencing data has shown no evidence of significant genetic change. Scientists at the Pasteur Institute said viral samples from Switzerland and France appear closely related.

Most hantaviruses spread through exposure to rodent urine, saliva or droppings, often in rural or wilderness environments. But Andes virus, first identified in Argentina and Chile in the 1990s, remains the only hantavirus known to transmit between humans.

Previous outbreaks have demonstrated how rapidly the virus can spread through clusters of human contact under certain conditions. One of the most closely studied examples occurred in the Argentine town of Epuyn in 2018, where a birthday party later became linked to a major outbreak.

Roughly 100 people attended the gathering, and dozens later contracted the virus.

Eleven people eventually died during the outbreak. Health investigators concluded that one infected attendee had unknowingly spread the virus to others during close social interactions, making the Epuyn outbreak a key case study in understanding Andes virus transmission.

GLOBAL MONITORING INTENSIFIES

The current outbreak has triggered an unusually coordinated international response involving the WHO, European health agencies and national governments. More than 100 passengers from over 20 countries have undergone monitoring, quarantine or medical evaluation after leaving the ship.

In the US, evacuees were transported to specialised biocontainment facilities in Nebraska, while the UK has flown exposed nationals from remote South Atlantic territories for precautionary isolation.

Despite growing concern, WHO officials continue to stress that the overall risk to the public remains low. Experts note that even in documented Andes virus outbreaks, sustained community transmission has remained uncommon.

Independent virologists also maintained that so far there is no clear evidence of the virus getting better at transmission between people – like SARS CoV 2, the virus behind COVID-19 pandemic.

Veteran virologist Dr Shahid Jameel underlined the cruise ship is really an isolated system, and it's sort of like putting people in a room and closing the windows.

“Also, though I dont know the exact details of anyone catching the infection on a flight, a flight cabin is also a closed environment with most of the air in it being recirculated..someone sitting very close to an infected person carries a high risk of catching infection,” the virologist, a research fellow with the Green Templeton College with University of Oxford told India Today.

Still, the emergence of infections beyond the immediate confines of the cruise ship – including the British-linked case and multiple international contacts now under observation – has reinforced concerns about the uncertainties surrounding one of the world’s least understood zoonotic diseases.

Currently health agencies are focusing on aggressive contact tracing, isolation and genomic analysis as they attempt to determine whether the outbreak represents a contained cluster or an indication of broader transmission risks that require closer scrutiny.

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