What is hantavirus, which has caused three deaths on a cruise ship

BarcelonaCape Verde has denied entry to a luxury cruise ship with about 150 people on board to protect "national public safety". This is how the African country's authorities have responded to the hantavirus outbreak detected on the tourist vessel, owned by the Dutch company Oceanwide Expeditions, where at least seven suspected cases have been detected, according to the World Health Organization, the WHO. Of these, only two have been confirmed by laboratory; however, to date, three people have died on board with similar symptoms and a fourth is in critical condition.

The ship left the Argentine port of Ushuaia, was heading to Cape Verde and had the Canary Islands as its final destination. In fact, the possibility of disembarking in Las Palmas de Gran Canaria or Tenerife to carry out new medical examinations on the travelers is now being considered. A total of 147 people were traveling on the cruise: 88 passengers and 59 crew members. In total, there are people of 23 different nationalities, among whom are 13 passengers and one crew member of Spanish nationality. Of these, five reside in Catalonia.

But what is hantavirus? Is this outbreak a concern for health authorities?

Hantavirus is the name given to a group of viruses that are mainly transmitted by inhalation of particles of urine, excrement, or saliva from rodents —such as field mice and voles— that have been previously infected, which is why enclosed or poorly ventilated spaces pose a potential focus of spread. It is rare for these viruses to spread between people, except in very specific cases with some variants, but if it does occur, it can lead to severe respiratory illnesses, such as the cases detected on the cruise.

Epidemiologist Charlotte Hammer from the University of Cambridge distinguishes hantaviruses that affect humans into two categories according to their possible origin. "Old World hantaviruses are found in Europe and Asia, while New World hantaviruses are found in America. In the current case, it is most likely to be the Andes virus, present in Argentina," she states in statements to SMC. The difference is mainly in organ involvement: while the former primarily affect the kidneys, the latter can cause severe lung infection and hemorrhages.

Low general risk

Initially, the symptoms of a hantavirus are like those of the flu —fever, headache, muscle aches, fatigue, and nausea—, but in severe cases, breathing difficulties, drops in blood pressure, or kidney problems may occur. In the case of New World hantaviruses, Hammer estimates that the fatality rate can rise to 40% in the absence of specialized medical care, while the other group remains around 10%.

The affected cruise ship set sail on March 20 from Argentina, and the route included continental Antarctica, the Falkland Islands, South Georgia Islands, Rossinyol Island, and Tristan da Cunha Island. One of the infected individuals was able to disembark in Cape Verde because they required urgent medical attention and were hospitalized in an intensive care unit (ICU).

The user @jakerosmarin, a passenger on the cruise ship, has posted a video on social media where they assure that what they are experiencing "is very real" and that they are people "with people waiting for them at home." Visibly emotional, they stated that the only thing those on board want is to "feel safe, get clarity, and get home":

"Although these diseases are potentially fatal, most hantavirus infections do not progress to this stage of the disease, and this is more likely to occur in people with underlying pathologies," adds Liam Brierley, a researcher at the MRC-University of Glasgow's Centre for Viral Research.

This is corroborated by epidemiologist Salvador Peiró, from the Research Area in Health Services and Pharmacoepidemiology of the Foundation for the Promotion of Sanitary and Biomedical Research of the Valencian Community (FISABIO), who explains that isolated cases of hantavirus are usually detected in rural areas, such as the one that was identified at the end of 2024 in Berguedà. Also in statements to SMC, Peiró assures that "there is no general risk to the population wherever the boat goes".

This was also stated this Monday by Hans Henri P. Kluge, WHO Regional Director for Europe: "The risk to the general population remains low. There is no reason for panic or to impose travel restrictions."

Regarding the origin of the outbreak, epidemiologist Salvador Peiró believes there is a common source of exposure: either before boarding the boat, as hantavirus symptoms take between two and four weeks to appear after infection, or in some area of the boat contaminated by mouse droppings. However, the long incubation period – from one to eight weeks – could make it difficult, for the moment, to determine exactly when and where the outbreak originated.

A month and a half of travel

After Cape Verde's refusal to allow the ship to dock, the company says preparations are being made for a possible medical repatriation of those affected, but that the disembarkation of passengers, medical evacuation, and medical examinations require the permission and coordination of local health authorities.

Once ashore, experts explain that all passengers will have to be monitored for the period in which they might develop symptoms and the ship will have to be cleaned and deratted.