MV Hondius: Hantavirus is on the rise in Argentina and scientists think they know why

Argentine officials and experts are scrambling to determine if their country is the source of a deadly hantavirus outbreak that has gripped Atlantic cruise, MV Hondius.

The health emergency aboard the vessel coincides with a surge of hantavirus cases in Argentina, which local public health researchers attribute to the recently accelerating effects of climate change. Argentina, the departure point for the Antarctic cruise, is consistently ranked by the World Health Organisation as having the highest incidence of this rare, rodent-borne disease in Latin America.

Experts suggest higher temperatures expand the virus’s range because, as it gets warmer and ecosystems change, hantavirus-carrying rodents can thrive in more places.

People typically contract the virus from exposure to rodent droppings, urine, or saliva. Hugo Pizzi, a prominent Argentine infectious disease specialist, stated: “Argentina has become more tropical because of climate change, and that has brought disruptions, like dengue and yellow fever, but also new tropical plants that produce seeds for mice to proliferate. There is no doubt that as time goes by, the hantavirus is spreading more and more.”

The Argentine Health Ministry on Tuesday reported 101 hantavirus infections since June 2025, roughly double the caseload recorded over the same period the previous year. The Andes virus, a hantavirus found in South America, can cause a severe and often fatal lung disease known as hantavirus pulmonary syndrome. The disease led to death in nearly a third of cases last year, the ministry confirmed, up from an average mortality rate of 15 per cent in the five years before that.

Authorities have confirmed that passengers aboard the MV Hondius ship tested positive for the Andes virus.

Argentine officials say they’re trying to pin down where infected passengers traveled in the country before boarding the Dutch-flagged cruise liner in Ushuaia, a city in southern Argentina known as the end of the world. Once they know the itineraries, they say they will trace contacts, isolate close contacts and actively monitor to prevent further spread.

The U.N. health agency, or WHO, says that the first death on board, a 70-year-old Dutch man, happened on April 11. His 69-year-old wife, also Dutch, died on April 26. The third passenger, a German woman, died on May 2.

The virus can incubate for between one and eight weeks. That makes it hard to know whether the passengers contracted the virus before leaving Argentina for Antarctica on April 1; during a scheduled stop to a remote South Atlantic island; or aboard the ship.

The province of Tierra del Fuego, where the vessel docked for weeks before departing, has never seen a case of hantavirus. Before boarding, the Dutch couple went sightseeing in Ushuaia, and traveled elsewhere in Argentina and Chile, WHO said.

The Argentine government’s leading hypothesis is that the couple contracted the virus during a bird-watching outing in Ushuaia, according to two investigators who spoke on condition of anonymity because they were not authorized to brief the media as they sifted through still-fragmentary evidence. Authorities are also tracing the Dutch tourists’ footsteps through the forested hillsides of Patagonia in southern Argentina where some infections are clustered.

Because early symptoms resemble the fever and chills of a flu, “tourists might think they just have a cold and not take it seriously. That makes it particularly dangerous,” Raul González Ittig, genetics professor at the National University of Córdoba and a researcher at state science body CONICET, said.

On Tuesday, the mountain resort town of Bariloche, Patagonia’s most common northern entry point, recorded its first human hantavirus case of 2026, the government of Río Negro Province said. He was hospitalized on Wednesday.

Argentina in recent years endured a historic drought. But it also had bouts of unexpectedly intense rainfall, part of a broader pattern of wild weather that scientists attribute to climate change.

Some of this variability has created conditions that have allowed hantavirus to flourish, experts say. Dry spells drive animals out of their usual habitats in search of food and water. Huge amounts of rain lead to vegetation growth, scattering seeds that attract leaf-munching rodents.

“When precipitation increases, food availability increases, rodent populations grow, and if there are infected rodents, the chance of transmission between rodents — and eventually to humans — also increases,” Ittig said.

Although hantavirus cases once were limited to the southern reaches of Patagonia, now 83% of cases are found in Argentina’s far north, according to the Health Ministry. In January, the ministry issued an alert on several fatal hantavirus outbreaks, including in the most populous province of Buenos Aires.

“With the climate changing, the epidemiological picture has completely changed,” said Pizzi. “The ship may be an isolated case. But this virus isn’t going anywhere.”

What is hantavirus?

Hantavirus is mainly spread by contact with rodents or their urine, saliva or droppings, particularly when the material is disturbed and becomes airborne, posing a risk of inhalation.

People are typically exposed to hantavirus around their homes, cabins or sheds, especially when cleaning out enclosed spaces with little ventilation or going into areas where there are mouse droppings.

The WHO says that while rare, hantaviruses may spread between people.

The US Centers for Disease Control and Prevention began tracking the virus after a 1993 outbreak in the Four Corners region – the area where Arizona, Colorado, New Mexico and Utah meet.

It was a doctor with the Indian Health Service who first noticed a pattern of deaths among young patients, said Michelle Harkins, a pulmonologist with the University of New Mexico Health Sciences Center who for years has been studying the disease and helping patients.

Most US cases are in Western states. New Mexico and Arizona are hotspots, Dr Harkins said, likely because the odds are greater for mouse-human encounters in rural areas.

Symptoms of hantavirus

An infection can rapidly progress and become life-threatening. Experts say it can start with symptoms that can include:

“Early in the illness, you really may not be able to tell the difference between hantavirus and having the flu,” said Dr Sonja Bartolome of UT Southwestern Medical Center in Dallas.

Symptoms of hantavirus pulmonary syndrome usually show between one to eight weeks after contact with an infected rodent. As the infection progresses, patients might experience tightness in the chest, as the lungs fill with fluid.

The other syndrome caused by hantavirus — hemorrhagic fever with renal syndrome — usually develops within a week or two after exposure.

Death rates vary depending on which hantavirus causes the illness. Hantavirus pulmonary syndrome is fatal in nearly 40 per cent of people infected, while the death rate for hemorrhagic fever with renal syndrome varies from 1 per cent to 15 per cent of patients, according to the CDC.