Explainer: What is the hantavirus that killed three cruise ship passengers?

Three people have died in an outbreak of hantavirus aboard a luxury cruise ship, with another five confirmed or suspected cases reported, but the World Health Organization has said the wider threat to public health remains low.

WHAT HAS HAPPENED ON THE CRUISE SHIP?

There have ​been eight known and suspected hantavirus cases linked to the cruise ship, the MV Hondius, the WHO said on Wednesday, including the three deaths.

Three people ‌were evacuated from the ship on Wednesday, two of them seriously ill, said the vessel’s operator Oceanwide Expeditions. Another patient remains in intensive care in South Africa, and a man who returned to Switzerland after being a passenger on the ship is being treated in Zurich.

There are nearly 150 people still on board the ship, which has been marooned off Cape Verde since Sunday and was expected to set off for Spain’s Canary ​Islands later on Wednesday.

Passengers who are not showing symptoms – currently all of those still on the ship – will be allowed to disembark when they reach the Canary ​Islands. Spain said the 14 Spanish passengers would be quarantined in a military hospital, while all other passengers will be repatriated and quarantined in ⁠line with their own countries’ guidance.

WHAT IS HANTAVIRUS?

Hantaviruses are rodent-borne viruses that can infect people and cause illness. The WHO estimates there are 10,000 to 100,000 human cases globally each year, ​with severity varying by strain.

The strain identified on the ship is the Andes hantavirus, which typically circulates in Argentina and Chile. The Hondius set off from Argentina on April 1.

HOW IS THE ​VIRUS SPREAD?

Hantavirus spreads primarily through rodents, infecting people via contact with rats or mice, or their urine, droppings, or saliva — often when the virus becomes airborne during cleaning of infested areas. Less commonly, it spreads through contaminated surfaces.

The Andes virus is the only known hantavirus that can spread through close, prolonged human-to-human contact.
The WHO said on Wednesday it had not been informed of any changes in the virus that could have made it more transmissible ​in this way, but it believes there has been some human-to-human spread on board the Hondius.

Studies have shown that the virus tends to transmit in the early stages of a ​patient’s sickness, when they have symptoms.

Maria Van Kerkhove, WHO Director of Epidemic and Pandemic Management, told Reuters in an interview on Wednesday that close contact meant something like sharing a cabin or bunk room ‌on board ⁠the ship. She said experts were working to establish which passengers were high-risk or low-risk, based on their contacts with passengers who were unwell.

WHAT ARE THE SYMPTOMS OF INFECTION?

Hantaviruses common in different parts of the world cause different symptoms or diseases — and some cause none at all.

Symptoms typically begin one to eight weeks after exposure and may include fever, muscle aches and gastrointestinal issues, according to the WHO, although a typical incubation period would be closer to around two to three weeks, said Andrew Pollard, a professor at Oxford University’s Pandemic Sciences Institute.

The Andes hantavirus and ​other hantaviruses in the Americas can cause hantavirus ​cardiopulmonary syndrome, which progresses quickly and leads ⁠to fluid buildup in the lungs along with heart complications. Fatality rates from hantavirus cardiopulmonary syndrome are up to 50%, the WHO says, compared to 1-15% from the infections common in Asia and Europe.

CAN HANTAVIRUS INFECTION BE TREATED?

There is no specific treatment for infection from hantavirus, so ​current therapy focuses on supportive care, including rest and fluids. Patients may need breathing support such as a ventilator.

Prevention focuses on limiting ​contact with rodents through measures ⁠like keeping areas and surfaces clean.

During outbreaks, contact tracing can give others potentially exposed to the virus earlier access to hospital care, improving outcomes and preventing further spread.

WHAT ARE THE RISKS TO THE GENERAL PUBLIC?

The cruise ship outbreak is unusual, although disease outbreaks of illnesses such as influenza are more common on ships due to proximity of people on board, experts said.

The current outbreak is being investigated by experts ⁠from the ​WHO and various countries but the risk to the public remains low, the U.N. health agency says.

Pollard said that knowing which virus ​was causing the outbreak meant it could be managed using public health protocols on the ship – such as containment and isolation – and in countries with returning passengers.

More broadly, hantaviruses continue to circulate worldwide, with the WHO warning of ​a rise in cases in the Americas in late 2025.