What is hantavirus?

Three people have died on a cruise ship in the Atlantic, reportedly from hantavirus. The disease has been confirmed in another traveller. What are the symptoms of the virus, and how does infection occur?

Three travellers have died aboard a cruise ship sailing from Argentina to Cape Verde. There is a suspected hantavirus infection. Another traveller has tested positive for the virus. According to media reports, the 69-year-old is receiving intensive care treatment in South Africa. Two crew members have also fallen seriously ill.

How and where exactly the travellers were infected remains unclear.

"The risk to the general public remains low," the WHO's European regional office said in a press release Monday. "There is no reason for panic or travel restrictions."

The ship involved is the "Hondius," operated by Dutch company Oceanwide Expeditions. There are currently 149 passengers and crew members on board.

What is hantavirus and how does infection occur?
Hantavirus is a zoonotic disease, meaning it is transmitted from animals to humans. Person-to-person transmission has not been observed in Europe.

In South America, a small number of cases of human-to-human transmission have been documented involving the Andes virus, a hantavirus strain found in Argentina and Chile — currently the only known variant capable of spreading between people. However, a 2021 study found that even person-to-person transmission of the Andes virus has not been definitively established.

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 faeces.

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 haemorrhagic 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 haemorrhagic 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 neutralised 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.