Hantavirus Cases on Dutch Cruise Ship Rise to Five; WHO Says Outbreak Is Not a Pandemic

On April 1, 2026, the MV Hondius — a Dutch-flagged polar expedition vessel operated by Oceanwide Expeditions — departed Ushuaia, Argentina, carrying approximately 150 passengers and crew bound for an Antarctic wildlife voyage [1]. Within ten days, a passenger was dead. Within five weeks, the ship had become an international incident: three dead, five confirmed infections, a dozen countries scrambling to trace former passengers, and the World Health Organization fielding questions about whether this was the beginning of another pandemic [2].

It was not. But what happened aboard the Hondius raises questions that extend well beyond this single vessel — about how 37 million cruise passengers per year move through regions harboring dangerous zoonotic pathogens, about who has authority to quarantine a ship when disease strikes in the middle of the Atlantic, and about whether the international health regulations designed to prevent exactly this kind of scenario are adequate to the task.

The Outbreak: Timeline and Transmission

The index case — a Dutch passenger — likely contracted the Andes hantavirus (ANDV) before the ship even left Argentina. Argentine investigators told the Associated Press that the leading hypothesis is that the couple contracted the virus during a birdwatching excursion near Ushuaia, where ANDV is endemic in wild rodent populations [3]. Symptom onset among the seven identified cases ranged from April 6 to April 28, presenting as fever, gastrointestinal distress, and rapid progression to pneumonia, acute respiratory distress syndrome, and shock [2].

The first death occurred on April 11. The passenger's body was removed from the ship on April 24, when the Hondius stopped at the remote South Atlantic island of St. Helena [4]. His wife flew commercially from St. Helena to South Africa, where she collapsed and died in a Johannesburg hospital on April 26 [5]. A third death occurred aboard the ship on May 2.

Laboratory analysis by the National Institute for Communicable Diseases in South Africa and Geneva University Hospitals in Switzerland confirmed the pathogen as Andes hantavirus [6]. This identification is significant: among roughly 20 to 30 hantavirus species known to cause human disease, ANDV is the only one with documented human-to-human transmission capability [7].

WHO epidemic and pandemic preparedness director Maria Van Kerkhove acknowledged this dimension: "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" [8]. The European Centre for Disease Prevention and Control (ECDC) classified all individuals aboard as close contacts because of the ship's enclosed environment and shared spaces [9].

As of May 7, the WHO reported five laboratory-confirmed cases, with three additional suspected cases under investigation [2].

The 40 Who Left: A Contact Tracing Challenge

The most operationally consequential failure in the outbreak response centers on what happened at St. Helena on April 24. Between 29 and 40 passengers — the figures differ between Oceanwide Expeditions and Dutch authorities — disembarked from the ship before the hantavirus diagnosis was confirmed [10][5]. They left without contact tracing, scattering to home countries across at least a dozen nations [11].

The result is a sprawling, multinational search operation:

• United States: The CDC confirmed it is monitoring six Americans who disembarked. Two Georgia residents are under observation with no symptoms. One Arizona resident is asymptomatic. Officials in Virginia and California are also tracking former passengers [12].
• United Kingdom: The UK Health Security Agency said two British nationals who left at St. Helena are isolating at home. Contact tracing continues for a seventh UK-linked individual who had not yet returned [11].
• Singapore: Two men who traveled from St. Helena to South Africa and then home to Singapore were isolated at the National Center for Infectious Diseases and tested for hantavirus [11].
• Switzerland: Health authorities confirmed one case linked to the ship — a passenger now being treated in Zurich [13].
• Spain: Fourteen passengers were placed in 45-day quarantine at the Hospital Central de la Defensa Gómez Ulla in Madrid, a facility established after the 2014 Ebola outbreak [5].

The flight attendant question added another layer: a Dutch flight attendant was hospitalized in the Netherlands and tested for hantavirus, though it remained unclear whether she had served on a KLM flight from Johannesburg to Amsterdam that may have carried an infected passenger [12].

Whether the St. Helena departure constituted a procedural failure or an authorized decision remains contested. At the time, no confirmed hantavirus diagnosis existed — the first laboratory confirmation came on May 2, more than a week later. Under the International Health Regulations (IHR 2005), flag states and port states share responsibility for health measures on vessels, but enforcement authority on a Dutch-flagged ship anchored off a British Overseas Territory during an unconfirmed disease event occupies a legal gray zone [14].

Fatality Rates in Context

Hantavirus pulmonary syndrome (HPS) is rare but lethal. The current MV Hondius outbreak, with three deaths among seven identified cases, represents an approximate case fatality rate of 43% — consistent with the historical range for HPS, though the small case count makes precise comparison unreliable [15].

Source: CDC, WHO, NEJM

Data as of May 7, 2026CSV

The 1993 Four Corners outbreak — the event that first identified hantavirus pulmonary syndrome in the United States — killed 27 of 48 confirmed patients nationwide, a 56% fatality rate [16]. The 2012 Yosemite outbreak, caused by the Sin Nombre virus in contaminated tent cabins, killed three of ten confirmed cases (30%) [17]. In the 2018-2019 Argentine ANDV cluster — the most directly comparable precedent — the case fatality rate was approximately 35% [18].

The decline in fatality rates over time reflects improved clinical recognition and earlier supportive care rather than differences in viral virulence. The MV Hondius cases progressed rapidly to acute respiratory distress syndrome, consistent with the typical ANDV clinical profile [2]. The ship's remote location likely delayed optimal medical intervention, which may partly account for the elevated fatality rate in this cluster.

The WHO's Assessment — and Its Critics

The WHO's position has been unequivocal. "This is not SARS-CoV-2. This is not the start of a Covid pandemic," Van Kerkhove told reporters on May 7 [8]. WHO Director-General Tedros Adhanom Ghebreyesus reinforced this, telling AFP the outbreak "does not resemble the early stages of the Covid-19 pandemic" [19].

The epidemiological basis for this assessment rests on several factors. ANDV requires prolonged close contact for human-to-human transmission. The infectious window is short — approximately one day, peaking at fever onset [18]. In the 2018-2019 Argentine outbreak studied in the New England Journal of Medicine, the estimated reproductive number (R0) was 2.12 before control measures and fell to 0.96 after isolation and contact tracing were implemented [18]. The ECDC assessed the risk to EU/EEA populations as "very low," citing the absence of ANDV's natural rodent reservoir in Europe and the expected effectiveness of standard infection prevention protocols [9].

Michael Osterholm, director of the University of Minnesota's Center for Infectious Diseases Research and Policy, supported this assessment: "It's not the next pandemic. This is one where everyone should just take a breath and know that we are going to bring this to resolution" [20].

But the WHO's reassurances land in a post-COVID information environment where institutional credibility is a finite resource. The organization's January 2020 statement that there was "no clear evidence of human-to-human transmission" of SARS-CoV-2 — issued while evidence was accumulating in Wuhan — remains a reference point for critics who argue that WHO risk assessments systematically understate novel threats [21].

The steelman case for skepticism is not that hantavirus will become the next pandemic. The biology makes that unlikely. It is that the WHO's binary framing — pandemic or not — obscures the operational risks that fall between those poles. An R0 of 2.12 before control measures, combined with 29 to 40 untraced passengers dispersed across a dozen countries, creates a scenario where localized clusters could emerge in settings far from the original exposure. If cases surface among disembarked passengers in the coming weeks, the question will not be whether ANDV has pandemic potential but whether the "low risk" designation led to insufficient urgency in the contact tracing response.

Martin Cetron, former director of the CDC's Division of Global Migration and Quarantine, addressed this nuance: "You could have a rare consequential big event that is unusual and it can be terrifying in the story you hear about it. But that is not necessarily the same as finding something which is exceedingly contagious via an airborne route" [20].

Maritime Health Regulations: A System Under Strain

The MV Hondius incident exposed friction points in the international framework governing disease response at sea. Under the IHR (2005), ships are required to carry a Ship Sanitation Certificate, subject to inspection every six months, covering rodent control, food safety, water quality, and waste management [14]. The International Maritime Organization (IMO) sets complementary standards for vessel hygiene.

Whether the Hondius passed its most recent sanitation inspection — and what that inspection covered regarding rodent prevention in the context of an expedition vessel visiting remote, wildlife-rich regions — has not been publicly disclosed. Argentina's health ministry announced it would conduct rodent capture and analysis in Ushuaia following the outbreak [3], suggesting that the exposure may have occurred onshore rather than from an onboard infestation.

The quarantine saga itself illustrated jurisdictional complexity. After the ship left St. Helena, it headed for Tenerife in Spain's Canary Islands, where regional president Fernando Clavijo rejected the vessel [1]. Cape Verde initially hosted the ship but did not permit passengers to disembark [22]. Spain's central government ultimately overruled Canary Islands authorities, directing the ship to dock for medical evacuation [13]. Three critically ill patients were evacuated during the transit, and Oceanwide Expeditions dispatched two Dutch infectious disease specialists to join the vessel [14].

Throughout this period, roughly 150 people remained confined to their cabins on a ship that was never designed for quarantine. The situation echoed the Diamond Princess in 2020 — another case where a cruise ship became a de facto isolation facility with no clear authority dictating the terms.

Zoonotic Risk and the Cruise Industry's Blind Spot

The cruise industry carried a record 37.2 million passengers in 2025, up from 34.6 million in 2024, and CLIA projects the number could reach 42 million by 2028 [23].

Source: CLIA State of the Cruise Industry Reports

Data as of May 7, 2026CSV

Disease outbreaks on cruise ships are not new. The CDC's Vessel Sanitation Program recorded 23 gastrointestinal illness outbreaks on cruise ships in 2025 alone, overwhelmingly caused by norovirus [24]. But those outbreaks involve pathogens adapted to human-to-human spread in enclosed environments. The Hondius case is different: a zoonotic pathogen, contracted from environmental exposure in a region with endemic rodent-borne disease, that then spread aboard a vessel.

This distinction matters because public health modeling for cruise ship disease risk has historically focused on respiratory and gastrointestinal pathogens that circulate among passengers. Zoonotic spillover events — where a passenger contracts a pathogen from wildlife or environmental exposure at a port of call and then introduces it to the ship population — represent a risk category that expedition cruising amplifies. Vessels like the Hondius visit Antarctica, sub-Antarctic islands, Arctic regions, and tropical forests specifically because of their wildlife — which also means passengers have direct or proximate contact with animal populations harboring pathogens rarely encountered in conventional travel [25].

Florian Krammer, a virologist at Mount Sinai, captured the knowledge gap: "Three days ago, nobody knew what a hantavirus was. I think that's part of it" [20]. STAT News noted that scientists are concerned less about pandemic risk than about the broader implication: hantaviruses remain understudied relative to their clinical severity, and this outbreak may represent a signal about emerging zoonotic risk in mobile, enclosed travel environments that existing surveillance systems are not designed to detect [20].

What Happens Next

As of May 7, the MV Hondius was expected to arrive at the Canary Islands within days for full passenger evacuation [13]. Seventeen American passengers remain aboard and are expected to be evacuated under U.S. State Department coordination [12]. All disembarking passengers will undergo diagnostic testing via serology or PCR before release, per ECDC recommendations [9].

The contact tracing operation for former passengers continues across at least a dozen countries. The ANDV incubation period can extend to 42 days, which is why Spanish authorities imposed a 45-day quarantine on the 14 passengers in Madrid [5]. The full epidemiological picture — including whether any of the disembarked passengers develop symptoms — will not be clear until at least mid-June.

The WHO's "low risk" assessment may well prove correct. The biology of Andes hantavirus — short infectious window, requirement for close contact, no airborne transmission — makes large-scale spread unlikely. But the MV Hondius outbreak has already demonstrated something the risk assessment does not capture: when a zoonotic pathogen enters a mobile, multinational population with no pre-existing surveillance framework, even a low-R0 virus can generate a response crisis that outstrips the disease itself.

The question is not whether hantavirus will cause the next pandemic. It will not. The question is whether the systems designed to contain infectious disease aboard ships — the IHR framework, port state quarantine authority, flag state responsibility, and cruise operator biosecurity — are adequate for an era in which 37 million passengers per year move through environments where novel zoonotic exposure is not an aberration but a feature of the itinerary.