On a cruise ship sailing from Argentina to Cape Verde, three passengers—a Dutch couple and a German woman—have died following a suspected hantavirus outbreak. The virus has been confirmed in another passenger. According to media reports, the 69-year-old is receiving intensive care treatment in South Africa. Several crew members are also seriously ill. The World Health Organization (WHO) estimates a total of eight hantavirus cases, three of which have been confirmed so far.

How and where exactly the travelers were infected remains unclear.

"The risk to the general public remains low," the WHO Regional Office for Europe said in a  press release on Monday. "There is no reason for panic or travel restrictions."

On Wednesday, it was reported that the deceased Dutch woman and the patient currently being treated in South Africa were infected with the Andes virus. Although rare, this is the only strain of hantavirus known to spread from person to person, and it has a higher mortality rate than most others.

The ship involved is the "Hondius," operated by the Dutch company Oceanwide Expeditions. A total of 149 passengers and crew were on board.

What is hantavirus and how does infection occur?

Hantavirus is a zoonotic disease, meaning it is typically transmitted from animals to humans. The exception is the Andes virus, which is believed to be capable of human-to-human transmission, although close, prolonged contact is usually required. This strain occurs in Chile and Argentina, where the cruise passengers are thought to have been infected. 

The natural hosts of hantaviruses are primarily various species of mice and rats, though the viruses have also been detected in shrews, moles and bats. Infected animals shed the virus through saliva, urine and feces.

People become infected through contact with the excretions of infected rodents. The most common way is breathing in contaminated dust — for example, when dried droppings or nesting material get stirred up.

Infection can also occur by ingesting contaminated particles or by touching the eyes or nose after contact with contaminated material. The virus can survive in the environment for several weeks. Direct contact with infected rodents is not necessary for transmission, though a bite from an infected animal can also cause infection.

What are the typical hantavirus symptoms?

The severity of illness depends on the hantavirus strain involved. Strains found in Europe and Asia typically cause flu-like illness, with high fever lasting three to four days (above 38 degrees Celsius or 100.4 degrees Fahrenheit), along with headache, abdominal pain and back pain — though some patients show no symptoms at all. In some cases, the disease can progress to hemorrhagic fever with renal syndrome, which can cause a drop in blood pressure and kidney dysfunction, potentially progressing to acute kidney failure.

The fatality rate of hemorrhagic fever with renal syndrome ranges from less than 1% up to 15%, depending on the virus strain, according to a 2023 review published in The Lancet.

Hantavirus strains found in North and South America can trigger a pulmonary syndrome, in which fluid accumulates in the lungs, blood pressure drops, and severe respiratory distress can develop. The pulmonary syndrome is fatal in roughly 30% to 40% of cases, according to the Lancet study.

Hantavirus in Germany

Hantaviruses have been known in Germany for many years, with between 200 and 3,000 cases typically reported annually.

The most common hantavirus strain in Germany is the Puumala virus, for which the bank vole is the primary reservoir host. According to the study from The Lancet, the mortality rate for this strain is around 1%.

Human infections with Dobrava-Belgrade virus have also been documented in Germany. While Puumala virus is found exclusively in western Germany, Dobrava-Belgrade virus is confined to eastern Germany, where its reservoir host, the striped field mouse, is present.

The Seoul virus is also an occasional cause of hantavirus infection in Germany.

Long-term effects and treatment

Recent studies suggest hantavirus can have lasting health consequences even after the acute infection resolves. Researchers have found that patients face an elevated risk of certain blood cancers and cardiovascular diseases in the years following infection. The underlying mechanisms remain unclear, according to the Lancet study.

Treatment for hantavirus is largely limited to managing symptoms. Severe cases may require dialysis or mechanical ventilation. No vaccines against hantavirus are currently available in Europe, North America or South America. Vaccines are used in China and South Korea, but their efficacy has not yet been scientifically confirmed, according to the study from The Lancet.

Research into new treatment approaches is ongoing. An experimental therapy based on antibodies from survivors successfully neutralized several hantavirus strains in initial trials. Separately, DNA vaccines targeting Puumala virus showed promising results in early human trials, with findings published in November 2024.

This article was originally published in German.

Editor's note: This article was originally published on May 5. We updated it on May 6 with new information on the deceased and ill passengers. On May 7, we added information on the confirmed cases of the Andes virus.