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A person who was aboard the cruise ship MV Hondius has tested positive for a variant of hantavirus and is now in an intensive-care unit in South Africa.Credit: Elton Monteiro/EPA/Shutterstock

Infectious-disease researchers are eager to learn more about a suspected outbreak of hantavirus, on a cruise ship in the Atlantic Ocean. Three people have died while on board the MV Hondius and a fourth passenger has been evacuated to a hospital in South Africa. The World Health Organization says laboratory testing has confirmed that this person has a variant of hantavirus, a family of viruses that are carried by rodents but can also infect people.

In addition, two crew members have respiratory symptoms but have not been confirmed to have the infection, according to the ship’s operator, the Dutch company Oceanwide Expeditions. The cause of death for the other three passengers is not yet known, the company said in a statement. The MV Hondius is currently located off the coast of Cabo Verde.

Vaithi Arumugaswami, an infectious-disease researcher at the University of California, Los Angeles, says that hantaviruses do not pose a pandemic risk, but the incident is a warning that the viruses should be monitored and that more research is needed to develop vaccines and treatments for them.

What are hantaviruses?

There are two main groups of hantaviruses. The Old World hantavirus is found in Africa, Asia and Europe and causes haemorrhagic fever with renal syndrome (HFRS). The New World hantavirus has been found in the Americas and causes hantavirus pulmonary syndrome (HPS).

Arumugaswami thinks that the passenger on the ship was probably infected with a strain of the New World subgroup called the Andes virus, which was first identified in Chile and Argentina in 1995. This virus is concerning because it can spread between people, he says.

The MV Hondius started its journey in Argentina, which has had an ongoing outbreak of the Andes virus since last year. Between July 2025 and January 2026, at least 20 deaths from the virus were reported in the country. The number of cases has been similar to that in previous years, but researchers say there has been an increase in the fatality rate.

Between January 2025 and January 2026, 34% of people infected with the virus died, compared with the historical national averages of 10–32% in each year between 2019 and 2024, according to Argentina Ministry of Health.

How do hantaviruses spread?

Humans typically contract the virus by inhaling aerosolized droplets of rodent faeces, urine or saliva containing the virus. Human-to-human transmission is possible but rare.

Any outbreak on the ship probably resulted from contact with material from an infected rodent, rather than transmission between people, says Rhys Parry, a molecular virologist at the University of Queensland in Brisbane, Australia. Several people could have been exposed through the same contaminated area, he adds.

More cases might emerge over the next few days or weeks, says Parry, because symptoms often start between a week and a month after exposure. This means that passengers or crew members could have contracted the disease before they boarded, during offshore trips or on board.

Arumugaswami says that the ship departed from Ushuaia in southern Argentina, which is more than 1,500 kilometres from the areas where the virus is known to be circulating. This could also mean that the passenger with the infection contracted the disease while travelling in Argentina before boarding, or that the virus is circulating undetected in the southernmost regions of the country, he adds.

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doi: https://doi.org/10.1038/d41586-026-01450-7

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