BY: Attila J. Hertelendy, PhD1,2Lawrence O. Gostin, JD3Gregory R. Ciottone, MD2,4
The Andes hantavirus outbreak aboard the expedition vessel MV Hondius is likely to remain limited. Yet the fragmented international response reveals a deeper vulnerability in global health preparedness: despite major reforms after COVID-19, pandemic preparedness remains weakest not in scientific capability, but in operational authority and coordination across jurisdiction
The epidemiological timeline of the hantavirus outbreak aboard the Dutch-flagged Hondius underscores critical delays in detection and international notification. Following an April 1, 2026, departure from Ushuaia, Argentina, the index fatality occurred on April 11. The body remained onboard for 13 days until disembarkation at Saint Helena on April 24, following Hondius’ arrival on April 22, alongside a symptomatic spouse who subsequently traveled via commercial aircraft to Johannesburg, South Africa, dying on April 26. Formal notification of the cluster to the World Health Organization (WHO) by the UK did not occur until May 2—three weeks after the initial death—by which time 34 passengers and crew had already dispersed internationally.1 The US Centers for Disease Control and Prevention (CDC) issued a Health Alert Network advisory on May 8, 6 days after the WHO notification.2 Following the vessel’s arrival in Tenerife, Spain, on May 10, repatriation of all passengers was completed by May 11. As of May 20, the European CDC reported 10 cases (8 laboratory confirmed, 2 probable) and 3 deaths associated with the voyage (Figure).3
Per the European Centre for Disease Prevention and Control, as of May 20, 2026, there have been 10 cases (8 confirmed, 2 probable), 3 deaths, a 9-country IHR response, and a 42-day surveillance window; there have been no new cases since May 13, 2026.
CDC indicates US Centers for Disease Control and Prevention; HAN, Health Alert Network; IHR, International Health Regulations; WHO, World Health Organization.
Laboratory testing identified Orthohantavirus andesense (ANDV), a hantavirus endemic to Patagonia and the only known hantavirus capable of limited person-to-person transmission. Most hantaviruses are acquired by inhalation of aerosolized rodent excreta and do not spread between humans. ANDV outbreaks in Argentina and Chile have demonstrated transmission among household contacts, sexual partners, and unprotected caregivers exposed during close, prolonged interaction.4 Unlike SARS-CoV-2, ANDV has not demonstrated sustained airborne transmission in community settings.
The clinical consequences can nevertheless be severe. Hantavirus cardiopulmonary syndrome begins with fever, myalgia, and gastrointestinal symptoms and progresses in severe cases to pulmonary edema, respiratory failure, and shock, with case fatality of 35% to 50%.1,4 Incubation periods extend beyond 1 month, complicating cross-border surveillance and follow-up. Rigorous monitoring of exposed travelers and intensive supportive care for symptomatic patients are essential.
The principal vulnerability exposed by the Hondius outbreak lies not in sustained transmission, but in delayed recognition, fragmented authority, and inconsistent public health implementation across jurisdictions. The response failed at multiple levels.
The index death was not recognized as a possible infectious disease event, allowing exposed and symptomatic passengers to disembark and continue international travel before contact investigations began. Operational responsibility was fragmented among the vessel operator, the Dutch flag state, port states (Saint Helena, Cabo Verde, and Spain through the Canary Islands), passengers’ home countries, and WHO. No single entity possessed clear authority or operational capacity to direct a coordinated public health response.
Cabo Verde declined general disembarkation, citing limited health system capacity and concern about exposing the local population. Spain ultimately accepted the vessel at Tenerife. Clinically ill patients were evacuated to Europe and South Africa, while remaining passengers awaited repatriation; the CDC coordinated repatriation of US passengers to the National Quarantine Unit at the University of Nebraska Medical Center.2 WHO recommended active monitoring of exposed travelers for 42 days,2 but implementation depended on national authorities with varying surveillance capacities, legal frameworks, and clinical thresholds for testing, isolation, and quarantine.
Cruise ships uniquely expose these weaknesses because they compress globalization into a single mobile environment: multinational passengers disembarking at multiple ports, overlapping jurisdictions, prolonged close contact, and extensive onward travel. Once an outbreak emerges at sea, responsibility quickly becomes diffuse and politically contested. The COVID-19 pandemic illustrated these vulnerabilities during the Diamond Princess outbreak in 2020, when 3711 passengers and crew—more than 700 of whom became infected—remained quarantined off Yokohama, Japan, while governments struggled to coordinate disembarkation, medical care, and repatriation.5 The Hondius outbreak suggests many of those operational weaknesses remain insufficiently addressed.
Preparedness at the vessel level remains uneven. Cruise ships should be regarded not simply as floating hotels, but as mobile outbreak platforms requiring core public health and medical capabilities. Vessels operating in regions of zoonotic disease risk should maintain robust rodent-control measures, modern sanitation systems, enhanced ventilation and filtration, onboard isolation and quarantine capacity, personal protective equipment, and protocols for rapid medical evacuation. Syndromic surveillance, specimen collection, and immediate notification procedures for unusual illness clusters or unexplained deaths should be standardized. Passenger manifests and cabin-level contact mapping should be continuously maintained to support rapid epidemiologic investigation when outbreaks occur.1
The Hondius outbreak also highlights persistent limitations in global health governance and law. With strong US support, WHO adopted amendments to the International Health Regulations (IHR) in 2024, the principal legal framework governing cross-border disease threats. The IHR require rapid detection, assessment, and notification to WHO of events that may constitute a public health emergency of international concern; increased transparency; and enhanced coordination among states and vessel operators. The IHR also require states to maintain core capacities at points of entry and establish sanitation and inspection measures for ships, including vector control, water and food safety, and onboard medical capabilities.
The IHR limit arbitrary denial of port entry and disembarkation (Article 28) while requiring that travelers be treated with dignity (Article 3) and according to evidence-based public health principles (Article 22). Yet while the IHR assign states substantial responsibilities, they afford WHO limited operational authority. WHO can coordinate information sharing, issue technical guidance, and recommend public health measures, but it cannot compel states to permit disembarkation, harmonize quarantine protocols, or share responsibility for exposed travelers.6 The result is a persistent asymmetry in global health governance: WHO is expected to coordinate international outbreaks without possessing the legal authority to ensure collective action.
Political tensions surrounding WHO further complicate outbreak prevention and response. The IHR reforms were intended to avoid another chaotic maritime crisis, yet President Donald Trump signed an executive order in January 2025 to withdraw the US from WHO and formally reject the IHR amendments. In the postpandemic period, political support for international law and cross-border cooperation appears to be weakening.
The first operational lesson from the Hondius outbreak is that cruise ships require far stronger baseline public health and medical capacities, including enhanced environmental controls, outbreak surveillance systems, onboard isolation capability, and standardized protocols for medical evacuation and disembarkation. Second, WHO member states should negotiate a dedicated maritime outbreak protocol under the IHR, clarifying responsibilities for port entry, quarantine, repatriation, and data sharing during multinational health emergencies. Third, governments should support WHO in developing coordinated passenger-tracing mechanisms for cross-border maritime outbreaks. Fourth, investment in point-of-entry capacities remains essential, particularly for lower-resource ports and small island states that may suddenly confront complex international health emergencies beyond their operational capabilities.
The Hondius outbreak will not become a pandemic. That is precisely why it matters. Preparedness should not be judged only by whether the world can respond to catastrophic global crises, but also by whether it can manage smaller, containable outbreaks before they escalate.7 The scientific tools to identify and characterize emerging pathogens are more advanced than ever. The persistent weakness lies elsewhere: in the ability of governments and international institutions to coordinate law, logistics, surveillance, and public health action across borders under conditions of uncertainty. On that measure, the international system remains dangerously deficient.
As published in JAMA : https://jamanetwork.com/journals/jama/fullarticle/2849730#251046447