Health authorities work to contain cruise ship hantavirus outbreak

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Daniel Pastula, University of Colorado Anschutz

(THE CONVERSATION) The MV Hondius, a Dutch cruise ship with a deadly outbreak of hantavirus, was on its way to the Canary Islands on May 7, 2026, after evacuating three ill passengers for treatment.

The World Health Organization confirmed the outbreak on May 4, noting a total of seven infections, with three deaths since the outbreak began in early April. An eighth case was confirmed on May 6.

Because of the illness’s one- to eight-week incubation period, additional cases may still be identified. Health officials around the world are monitoring passengers who disembarked from the ship in the early days of the outbreak in late April. Health officials emphasize, however, that the risk to the public from the outbreak is low.

I’m a medical epidemiologist – here’s what you need to know about the virus and how the outbreak is playing out.

What is hantavirus?

Hantavirus isn’t just one virus but a group of closely related viruses found throughout the world. Their natural reservoir is rodents, such as wild mice, rats and moles. Infected rodents don’t get symptoms, but the virus replicates in their cells. It sometimes spills over into other animals, including humans, and can cause severe disease and even death.

There are two general types of hantaviruses. Old World hantaviruses, typically found in Europe and Asia, generally affect the kidneys. Their mortality rate in people is 15% or less.

New World hantaviruses, such as the one causing the outbreak on the Hondius, occur in North and South America. The best-known strains of this type are the Andes virus, the strain that was confirmed in the cruise ship outbreak, and the Sin Nombre virus, which likely caused the death of Betsy Arakawa, Gene Hackman’s wife, in March 2025.

These viruses generally affect the lungs and are fatal in about 40% of cases. Symptoms start with a flu-like illness and can progress quickly to intense inflammation in the lungs that leads to lung and heart failure.

A person with a hantavirus infection may experience symptoms anywhere from a week to eight weeks after exposure. There is no treatment; doctors can offer only supportive care, such as hydration, artificial respiration or dialysis.

How do these viruses spread?

Cases of hantavirus infection are rare. The Centers for Disease Control and Prevention recorded 890 cases in the U.S. from 1993, when surveillance began, through the end of 2023.

The vast majority of cases occur in China, with thousands of cases caused by Old World hantavirus strains occurring annually.

Most often, people become infected with these viruses by inhaling aerosolized urine or droppings from infected rodents. Imagine a cabin infested with mice infected by the virus – sweeping the cabin would shake up dust from the mouse urine and droppings, distributing it through the air and enabling people to inhale the viral particles. There’s a smaller risk of getting ill through direct contact, such as by being bitten by an infected rodent or by touching its saliva.

The worry on the cruise ship is human-to-human transmission. Epidemiologists had previously found hints that the Andes virus may be transmitted from one person to another under certain circumstances, such as close, sustained contact in close quarters, like a small cruise ship.

What do investigators think happened on the cruise ship?

The Hondius, now carrying close to 150 passengers, started out in Argentina on April 1 and was sailing north on a 33-day journey.

There were no reports of rodents on the ship, so it’s unlikely the illness started there. According to news reports, the people who first got sick had been touring Argentina and Chile for months beforehand. Researchers speculate they likely got infected during an activity in which they were exposed to a rodent carrying the disease or its excrement.

Given these viruses’ weekslong incubation period, these people may have been feeling fine when they boarded the ship, before eventually falling ill. They may have then spread Andes virus to others through breathing shared air or other close contact in close quarters.

What happens now?

The ship is now traveling to Spain, and multiple patients are being evacuated along the way.

Also, researchers are tracking 29 people who disembarked from the ship on April 24, before the outbreak was identified. People who had significant exposure will likely be quarantined to watch for symptoms and be isolated if symptoms develop.

Residents of three U.S. states are being monitored. Dutch officials announced on May 7 that a flight attendant who was not a passenger but briefly interacted with a passenger was hospitalized with possible hantavirus symptoms.

Is the situation dangerous?

Health officials can’t rule out that additional hantavirus cases may emerge in the cruise ship outbreak, but beyond the ship the risk remains low. That’s because most cases of hantavirus, including Andes virus, are acquired directly from rodents or their excrement and not from other humans.

It’s important to note, however, that even on vacation, people should pay attention to risks for infection – particularly as they may be very different from the ones they’re used to at home.

This article is republished from The Conversation under a Creative Commons license. Read the original article here: https://theconversation.com/health-authorities-work-to-contain-cruise-ship-hantavirus-outbreak-282343.