The virus does not respect provincial boundaries, and neither do the animals that carry it.
Three deaths and thirteen illnesses aboard a cruise ship departing from the southern tip of Argentina have set in motion a widening search for the hidden ecological roots of hantavirus in South America. Scientists from Argentina and the United States are now turning their attention to Mendoza province, hundreds of kilometers from where the outbreak began, following the logic that a virus carried by wild rodents does not confine itself to the places where humans first notice it. The Andes strain — uniquely capable of passing between people — has long been endemic to the southern cone, and this investigation is an attempt to map the living landscape of a threat that exists whether or not it has yet announced itself.
- A cruise ship became an unlikely epicenter: thirteen people infected, three dead, and a pathogen with no vaccine and no cure at the center of it all.
- The Andes strain's rare ability to spread human-to-human elevates this beyond a typical zoonotic event, placing entire communities along a potential transmission chain.
- Early fieldwork in Tierra del Fuego captured over a hundred rodents but found none of the primary carrier species — a result that raised more questions than it answered.
- Researchers are now expanding the search to Mendoza, a province with no confirmed Andes cases but with ecological conditions that may already harbor the virus silently in local wildlife.
- Argentine and CDC scientists will cast a wider net, sampling three rodent species across sites chosen by ecological pattern — a methodical attempt to find the virus before it finds new victims.
In early April, the MV Hondius left Ushuaia bound for open waters. Weeks later, passengers and crew began falling ill with hantavirus — a rare and severe infection carried by rodents. Thirteen people were ultimately confirmed or probably infected; three died. The outbreak set off an investigation that has since grown well beyond the ship.
Argentine health officials announced that researchers from the Malbrán epidemiological center and the U.S. Centers for Disease Control and Prevention would launch a new phase of rodent surveillance in Mendoza province, far to the north of where the outbreak began. The virus responsible — the Andes strain — is the only known hantavirus variant capable of spreading directly between humans, and it circulates endemically across the southern regions of Chile and Argentina.
Earlier fieldwork in Tierra del Fuego had already captured more than a hundred rodents for analysis, yet none proved to be Oligoryzomys longicaudatus, the long-tailed rat species considered the primary carrier. Testing of those specimens was still ongoing. The Mendoza phase will broaden the search to include two additional species — Abrothrix hirta and Abrothrix olivacea — both associated with hantavirus transmission in the wild.
Mendoza has no confirmed history of Andes strain circulation among its human population, but researchers acknowledge the rodent reservoir may already be present, quietly waiting. The expanded surveillance is an effort to locate that invisible presence before it surfaces as illness — a recognition that in tracking zoonotic disease, the absence of reported cases is not the same as the absence of risk.
In early April, a cruise ship called the MV Hondius departed from Ushuaia, a port city at the southern tip of Argentina. Weeks later, passengers and crew began falling ill with hantavirus—a rare, severe infection spread by rodents. By the time health authorities finished counting, thirteen people had confirmed or probable cases of the disease. Three of them died. The outbreak triggered an urgent investigation that has now expanded far beyond the ship itself.
Argentine health officials announced Friday that experts from their country and the United States would launch a new phase of rodent surveillance in Mendoza province, a region hundreds of kilometers north of Ushuaia. The move represents a significant escalation in the effort to understand how the virus spread and whether it poses a broader threat to the population. Researchers from Argentina's Malbrán epidemiological center and the U.S. Centers for Disease Control and Prevention will lead the work, selecting study sites based on ecological patterns that match the habits of the rodents known to carry hantavirus.
The virus itself is transmitted by a long-tailed rat species called Oligoryzomys longicaudatus. It is uncommon, has no vaccine, and offers no specific treatment once infection takes hold. The particular strain detected on the cruise ship—known as Andes—is especially concerning because it is the only known variant capable of spreading directly from one human to another. This strain circulates in the southern regions of both Chile and Argentina, making the southern cone of South America a natural reservoir for the disease.
Investigators had already conducted fieldwork in May in Tierra del Fuego, the province containing Ushuaia. During that mission, they captured more than one hundred rodents for laboratory analysis. Surprisingly, they found no long-tailed rats among them, though testing of those specimens was still ongoing at the time of the announcement. The new work in Mendoza will cast a wider net, collecting samples not only from the long-tailed rat but also from two other rodent species—Abrothrix hirta and Abrothrix olivacea—both of which have been linked to hantavirus transmission in natural settings.
Mendoza province has not previously recorded confirmed cases of Andes strain hantavirus circulating among its population. Yet researchers from Mendoza University acknowledged that the rodent reservoir capable of carrying the virus may already be present in the region, even if the disease has not yet emerged there. This possibility—a dormant threat waiting in the local wildlife—is precisely why the expanded surveillance matters. By understanding which rodent populations carry the virus and where they live, health authorities can better predict where human cases might emerge and prepare accordingly.
The investigation reflects a fundamental challenge in tracking zoonotic diseases: the virus does not respect provincial boundaries, and neither do the animals that carry it. What began as a discrete outbreak on a ship has become a reason to examine the ecological landscape of an entire region, searching for the invisible presence of a pathogen that kills without warning and offers no cure.
Notable Quotes
Mendoza province has not registered confirmed circulation of Andes virus, but the potential presence of the rodent reservoir exists in the region.— Mendoza University
The Hearth Conversation Another angle on the story
Why expand the study to Mendoza if the virus hasn't shown up there yet?
Because the rodents that carry it might already be there. You don't wait for people to get sick to understand the risk.
But they found no long-tailed rats in Tierra del Fuego, where the ship actually departed. Doesn't that suggest the virus came from somewhere else?
It suggests we don't yet know where it came from. That's why they're still analyzing those hundred rodents they captured. The absence of evidence isn't evidence of absence.
Three people died. How does that happen if there's no treatment?
Once hantavirus takes hold in a human, there's no specific drug to stop it. You can only support the patient through the illness and hope their immune system wins. Some do. Some don't.
Is Mendoza in actual danger, or is this precautionary?
Both. The virus is endemic in southern Argentina and Chile. Mendoza hasn't seen it yet, but the conditions might exist there. Better to know what's in the rodent population now than to discover it through human illness later.
Who's most at risk—cruise passengers, port workers, or the general population?
Anyone who comes into contact with infected rodents or their droppings. That could be anyone, but people working outdoors or in storage areas are more exposed. The cruise ship outbreak was unusual precisely because hantavirus doesn't normally spread person to person. This Andes strain does.