WHO Says Hantavirus May Have Spread Between Passengers on Cruise Ship

A deadly hantavirus outbreak aboard a small expedition cruise ship in the Atlantic Ocean has killed three people, stranded nearly 150 others, and forced the World Health Organization to confront a question most virologists thought was settled: can hantavirus spread from person to person?

The MV Hondius, a Dutch-flagged vessel operated by Oceanwide Expeditions, departed Ushuaia, Argentina on April 1, 2026 on an island-hopping voyage across the South Atlantic [1]. By May 2, when WHO received formal notification through the International Health Regulations framework, two passengers were dead, one was critically ill, and the ship was adrift off the coast of Cape Verde with no port willing to accept it [2].

As of May 5, seven cases — two laboratory-confirmed by PCR and five suspected — have been identified, including three deaths, one critically ill patient, and three individuals with mild symptoms [1]. The case fatality rate among identified cases stands at 42.9%, exceeding the historical average for hantavirus pulmonary syndrome (HPS) in the United States (35%) and Argentina (21.4%), though the small sample size makes statistical comparison unreliable [3][4].

Source: CDC / WHO / Published Literature

Data as of May 4, 2026CSV

The Victims and the Voyage

The MV Hondius is a 107-meter expedition vessel designed for polar and remote-area cruises, carrying 88 passengers and 59 crew members — 147 people from 23 nationalities, including 17 Americans, 19 British nationals, 13 Spaniards, and 38 Filipino crew members [5][6][7].

The first patient, designated Case 1, was a 70-year-old Dutch man who developed symptoms on April 6, five days after the ship left Argentina [1][8]. He and his wife — Case 2, aged 69 — had traveled through South America, including Argentina, before boarding the cruise [1]. Case 1 died on April 11. His body was kept aboard the ship until it reached the remote island of St. Helena on April 24, where he was declared dead on arrival [8].

Case 2, his wife, disembarked and traveled to South Africa, where she collapsed at Johannesburg's O.R. Tambo International Airport and later died on April 26 [8]. Case 3, an adult British male, developed pneumonia on April 24 and was evacuated to a hospital in Johannesburg on April 27, where he was placed in intensive care but was reportedly improving [9]. Case 4, a German woman, developed pneumonia and died on board on May 2 [8][10]. Cases 5 through 7 presented with high fever and gastrointestinal symptoms between April 28 and the end of the month, and remained on the ship with mild illness [1].

Source: WHO Disease Outbreak News

Data as of May 4, 2026CSV

The clinical presentation across severe cases followed a consistent pattern: fever, gastrointestinal symptoms, rapid progression to pneumonia, acute respiratory distress syndrome (ARDS), and shock [1] — a textbook description of hantavirus pulmonary syndrome.

The Andes Virus Question

Hantaviruses are a family of viruses carried by rodents and transmitted to humans primarily through inhalation of aerosolized urine, droppings, or saliva from infected animals [4]. There are no approved vaccines and no specific antiviral treatments. The disease kills roughly 35-40% of those who develop the pulmonary syndrome [3][4].

Among the dozens of known hantavirus species, one stands apart: the Andes virus (Orthohantavirus andesense), found in Argentina and Chile. It is the only hantavirus with documented human-to-human transmission [1][11]. That transmission has historically been limited to close, prolonged contact — household members, intimate partners, and occasionally healthcare workers — and remains rare even in endemic areas [11][12].

WHO's official outbreak report states that the specific strain infecting passengers has not yet been publicly identified, though it notes that "Orthohantavirus andesense is responsible for most cases in South America" [1]. Viral sequencing is underway at a South African laboratory [6]. Given that the ship departed from Argentina — where Andes virus is endemic — and that Cases 1 and 2 had traveled through the country before boarding, Andes virus is the leading candidate.

The critical question is whether the genetic sequence, once published, will show mutations that might enhance human-to-human transmissibility, or whether it matches known rodent-reservoir strains. That answer is not yet available.

The Evidence for Human-to-Human Spread

WHO's Dr. Maria Van Kerkhove, director of epidemic and pandemic preparedness, stated on May 5: "We do believe that there may be some human-to-human transmission that's happening among the really close contacts, the husband and wife, people who've shared cabins" [6][13].

The epidemiological argument rests on several observations. Cases 1 and 2 were a married couple who shared a cabin and had traveled together in Argentina — a shared rodent exposure is plausible for both [1]. But Cases 3 through 7 are harder to explain through a common environmental source. The ship's operator has stated there were no rodents aboard [14]. The vessel visited several remote islands — mainland Antarctica, South Georgia, Nightingale Island, Tristan da Cunha, St. Helena, and Ascension Island — but hantavirus is not known to be endemic on any of them [1][14].

If no rodent source can be identified aboard the ship or at its ports of call, the remaining explanation is transmission from one infected person to others in the confined shipboard environment. The 22-day span of illness onset — April 6 to April 28 — is consistent with a chain of transmission given hantavirus's incubation period of one to five weeks [1][4].

Marion Koopmans, a virologist at Erasmus Medical Center in the Netherlands, told reporters that a cruise ship would be "an ideal setting" for human-to-human transmission of Andes virus, given the close quarters and prolonged contact between passengers [13].

The Skeptics' Case

Not all experts are persuaded. Kari Debbink, a virologist at the Johns Hopkins Bloomberg School of Public Health, called the evidence "compelling" but noted a key counterpoint: if the virus were transmitting efficiently between people on a ship where 147 individuals spent weeks in close proximity, "you would have a lot more cases" [6].

Seven cases out of 147 people in a confined environment over more than a month is not the attack rate expected from an efficiently transmitting respiratory pathogen. For comparison, the Diamond Princess COVID-19 outbreak in 2020 infected more than 700 of approximately 3,700 passengers and crew within weeks [15]. The low case count on the Hondius is more consistent with either very limited transmissibility or a point-source exposure that affected only a subset of passengers.

Angela Rasmussen, a virologist at the University of Saskatchewan's Vaccine and Infectious Disease Organization, cautioned against binary thinking: "People really do need to understand that there are different degrees of person-to-person transmission" [16]. A virus can be capable of occasional transmission between close contacts without posing a broader epidemic risk.

A 2022 systematic review published in PMC found that "the balance of the evidence does not support the claim that human-to-human transmission of hantavirus infection occurs" as a general phenomenon, though it acknowledged the specific exception of Andes virus in Argentina and Chile [12]. The bar for overturning the scientific consensus on hantavirus transmission routes requires genomic evidence of identical or near-identical viral sequences between epidemiologically linked cases, combined with exclusion of a common environmental source — criteria that have not yet been publicly met in this outbreak.

A Ship Without a Port

While the scientific investigation proceeds, 149 people remain in limbo. Cape Verde refused the Hondius permission to dock at the port of Praia as a precautionary measure [5]. For several days, the vessel sat anchored off the West African archipelago while diplomatic negotiations played out across multiple governments.

Under the International Health Regulations (2005), the flag state (the Netherlands), port states (Cape Verde, later Spain), and the affected states whose nationals are aboard all have obligations for information sharing and coordinated response [1]. The UK's National IHR Focal Point was the first to formally notify WHO on May 2 [1]. Authorities from Cape Verde, the Netherlands, South Africa, Spain, and the United Kingdom have since initiated coordinated response measures [1].

On May 5, the Spanish government announced that the Hondius could sail to the Canary Islands for a "full investigation" and "full disinfection," a decision made "in accordance with international law and the spirit of humanitarianism" [17][18]. WHO had formally requested, in coordination with the European Union, that Spain host the vessel [6]. Two passengers — reportedly the most critically ill remaining aboard — were being prepared for medical evacuation to the Netherlands [6].

Aboard the ship, conditions were described by passengers as manageable but tense. Travel blogger Jake Rosmarin, who was on the Hondius, stated that "the vessel is maintained to a very high standard, and suggestions that it is unclean are not accurate" [19]. He noted that the crew had implemented social distancing, mandatory masking, meal delivery to cabins, and restricted access to indoor common areas, while allowing outdoor deck access [19]. Oceanwide Expeditions received credit from passengers for keeping people "safe, informed and as comfortable as possible" [19].

Sanitation, Rodents, and Liability

The question of how hantavirus reached the ship remains unresolved. The operator says there were no rodents aboard [14]. Expedition vessels like the Hondius operate with strict biosecurity protocols, particularly when visiting ecologically sensitive regions like Antarctica and sub-Antarctic islands [19].

However, the ship visited Tristan da Cunha from April 13-15 [14], an island with known populations of introduced rodents, including mice. Nightingale Island, another stop, has also had rodent issues. Whether passengers had direct or indirect contact with rodent-contaminated environments during shore excursions has not been publicly addressed.

No public records of health inspection deficiencies for the MV Hondius have surfaced. The vessel was built in 2019 and is relatively new [20]. Legal liability questions — whether Oceanwide Expeditions, the flag state, or port authorities bear responsibility — depend on whether negligence can be established in sanitation, risk communication, or response timing. Those determinations are far from settled and will depend on the epidemiological investigation's conclusions about the source of infection.

What Confirmation Would Mean

If genomic and epidemiological evidence ultimately confirms human-to-human transmission of Andes virus aboard the Hondius, the implications extend beyond this single outbreak.

Emily Abdoler, an infectious disease specialist at the University of Michigan, noted that confirmed Andes virus human-to-human transmission changes the public health response calculus: it would require isolation protocols beyond simply removing rodent exposure [6]. For maritime health, it could prompt revisions to the WHO's International Health Regulations governing disease response on ships, potentially requiring enhanced respiratory screening at embarkation ports for vessels departing hantavirus-endemic regions.

WHO currently assesses the global population risk from this event as low [1]. That assessment reflects the historical rarity of human-to-human hantavirus transmission and the confined nature of the outbreak. But the organization's willingness to publicly state that human-to-human transmission "can't be ruled out" signals that the evidence is being taken seriously at the highest levels of global health governance [13].

The academic research community has already been tracking hantavirus transmission with increasing intensity. Over the past 15 years, more than 5,400 papers have been published on hantavirus transmission, peaking at 613 publications in 2023, according to OpenAlex data [21].

Source: OpenAlex

Data as of Jan 1, 2026CSV

Demographics and Risk Patterns

The available demographic data on the Hondius cases is limited but suggestive. The two confirmed initial cases — the Dutch couple aged 70 and 69 — are consistent with what is known about HPS risk factors: older adults with potential comorbidities face higher mortality [3][4]. The German woman who died (Case 4) has not had her age publicly disclosed. The British man in intensive care (Case 3) and the three mild cases (5-7) have limited public demographic details.

Expedition cruises like those offered by Oceanwide Expeditions tend to attract older, affluent travelers — a demographic that overlaps with higher-risk groups for severe HPS outcomes. Whether comorbidities such as cardiovascular disease, diabetes, or immunosuppression played a role in the fatal outcomes is not yet known. Land-based HPS outbreaks in the Americas have shown that while the virus can infect people of any age, mortality skews toward those over 50 and those with underlying health conditions [3].

The 23 nationalities represented aboard create a complex repatriation and follow-up challenge. Once passengers are cleared to leave, health authorities in their home countries will need to monitor them through the full incubation window — up to five weeks — to ensure no additional cases emerge [4].

An Unfinished Investigation

The Hondius outbreak remains in its early investigative stages. Critical pieces of evidence are outstanding: the complete viral genome sequence, the results of environmental sampling aboard the ship and at ports of call, detailed contact tracing among all 147 people aboard, and serological testing to determine whether additional asymptomatic infections occurred.

Until that evidence is assembled, the question of whether hantavirus spread between humans on this ship sits in an uncomfortable space between suspicion and proof. The WHO has been careful to say transmission "can't be ruled out" rather than that it has been confirmed [13] — a distinction that matters both scientifically and for the policy responses that would follow.

What is not in dispute: three people are dead, one remains critically ill, and 149 people spent weeks stranded on a ship in the Atlantic while nations debated who would let them ashore. However the transmission question resolves, the Hondius outbreak has already exposed gaps in the international system's ability to respond to disease events at sea — and raised questions about whether the world's health regulations are built for scenarios that don't fit neatly into existing categories.