Hantavirus is on the rise in Argentina, where a stricken cruise ship began its journey

Higher temperatures expand the virus’ range because, in part, as it gets warmer and ecosystems change, rodents that carry the hantavirus can thrive in more places, experts say. People typically contract the virus from exposure to rodent droppings, urine or saliva.

“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,” said Hugo Pizzi, a prominent Argentine infectious disease specialist. “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.

A hantavirus found in South America, called the Andes virus, can cause a severe and often fatal lung disease called hantavirus pulmonary syndrome. The disease led to death in nearly a third of cases in the last year, Argentina’s Health Ministry said, up from an average mortality rate of 15 in the five years before that.

Authorities said passengers on the MV Hondius ship tested positive for the Andes virus.

The cause of infection remains under investigation

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.

Climate change sends rodents to new frontiers

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.”