The Dutch cruise ship MV Hondius, grappling with a deadly hantavirus outbreak, was en route to the Canary Islands on May 7, 2026, after offloading three sick passengers for medical attention.

The World Health Organization verified the outbreak on May 4, reporting seven infections and three fatalities since it started in early April. An eighth case was identified on May 6.

Due to the virus's incubation period of one to eight weeks, more cases could still surface. Global health authorities are tracking passengers who left the vessel in late April, at the outbreak's onset. Officials stress that public risk from this event remains minimal.

As a medical epidemiologist, here is vital information on hantavirus and the current outbreak dynamics.

What is hantavirus?

Hantavirus refers to a family of related viruses present worldwide. Rodents like wild mice, rats, and moles serve as their primary hosts. These animals show no illness, yet the virus multiplies within their cells. It can occasionally jump to other species, including humans, triggering serious illness or death.

Hantaviruses fall into two main categories. Old World strains, common in Europe and Asia, primarily target the kidneys, with human fatality rates at 15% or lower.

New World variants, including the Andes strain behind the Hondius outbreak, prevail in the Americas. Notable examples include the Andes virus, confirmed in this incident, and the Sin Nombre virus, possibly linked to the March 2025 death of Betsy Arakawa, wife of Gene Hackman.

These strains mainly impact the lungs, proving lethal in roughly 40% of human cases. Initial flu-like symptoms can rapidly escalate to severe lung inflammation, resulting in respiratory and cardiac failure.

Symptoms of hantavirus may appear one to eight weeks post-exposure. No specific treatment exists; care is limited to supportive measures like fluids, mechanical ventilation, or kidney dialysis.

How do these viruses spread?

Hantavirus cases are uncommon. The U.S. Centers for Disease Control and Prevention logged 890 instances from 1993 through 2023.

China reports the bulk of cases, with thousands yearly from Old World strains.

Infection typically occurs via inhaling airborne particles from rodent urine or feces. For instance, cleaning a mouse-infested space could stir up contaminated dust, allowing viral inhalation. Lesser risks involve bites or contact with infected saliva.

On the cruise ship, concern centers on person-to-person spread. Past studies suggested the Andes virus might transmit between humans during prolonged close contact, such as in confined ship environments.

What do investigators think happened on the cruise ship?

The Hondius, now with about 150 passengers, departed Argentina on April 1 for a 33-day northward voyage.

No rodent sightings were noted aboard, making an onboard origin improbable. Initial patients had spent months exploring Argentina and Chile. Experts believe they contracted the virus during land activities involving rodent exposure or waste.

With the lengthy incubation, these individuals likely boarded symptom-free, only to sicken later and potentially infect others via shared air or proximity.

What happens now?

The vessel is proceeding to Spain, evacuating affected individuals en route.

Authorities are monitoring 29 who departed on April 24, prior to outbreak detection. High-risk contacts may face quarantine, with isolation if symptoms arise.

Residents in three U.S. states are under watch. On May 7, Dutch officials reported a flight attendant, non-passenger but briefly exposed, hospitalized with suspected symptoms.

Is the situation dangerous?

While more cases on the ship cannot be excluded, broader public risk stays low. Most hantavirus infections, including Andes, stem from rodents or their waste, not human contact.

Travelers should remain vigilant to unfamiliar infection hazards, even on leisure trips.