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Andes Hantavirus in 2026: What the Current Cruise-Ship Outbreak Means for Global Health

By Majid Sadigh, MD


The recent hantavirus outbreak linked to the expedition cruise ship MV Hondius has generated worldwide concern and revived memories of the early days of SARS and COVID-19. News that passengers traveled internationally before the illness was recognized has understandably raised anxiety among travelers and the public, especially because some exposed individuals returned to the United States, Canada, and several European countries before quarantine measures were fully implemented.


Hantaviruses are single-stranded, negative-sense, three-segmented RNA viruses that are usually carried by rodents and are most commonly transmitted to humans through contact with contaminated rodent urine, droppings, or saliva. People typically become infected after inhaling dust contaminated by infected rodents, often in cabins, barns, campsites, or rural environments. In most parts of the world, hantaviruses do not spread efficiently between people.


Hantaviruses found in the Western Hemisphere, including those in the United States, can cause hantavirus pulmonary syndrome (HPS), a severe respiratory illness characterized by fever, pulmonary edema, respiratory failure, and shock. The most common hantavirus responsible for HPS in the United States is Sin Nombre virus, which is carried primarily by the deer mouse (Peromyscus maniculatus). Importantly, unlike Andes virus, Sin Nombre virus is not known to spread from person to person. In essentially all recognized U.S. cases, transmission represents zoonotic spillover from infected rodents to humans, and the chain of transmission ends with the infected individual. Since HPS was first recognized in the United States in 1993, more than 900 confirmed cases have been reported, with a case-fatality rate of approximately 35%–40%.


At the center of the current concern is Andes virus, a hantavirus found primarily in Argentina and Chile. Clinically, Andes virus infection resembles Sin Nombre virus infection, producing severe HPS with a reported mortality rate of approximately 40%–45%. Unlike most hantaviruses, however, Andes virus has demonstrated limited human-to-human transmission under conditions of prolonged close contact. This characteristic has made the current outbreak particularly important from a global health perspective.


At present, no licensed vaccine, proven antiviral therapy, or validated pre- or post-exposure chemoprophylaxis exists for Andes hantavirus infection. Infection-control measures currently emphasize standard and droplet precautions for suspected cases, careful monitoring of close contacts, and avoidance of rodent-contaminated environments in endemic regions. Current evidence does not support widespread community masking recommendations because efficient casual airborne transmission has not been demonstrated. For most individuals, routine hand hygiene and standard respiratory precautions remain appropriate. Additional protective measures, including personal protective equipment (PPE) and airborne precautions, are mainly recommended for symptomatic patients, healthcare workers caring for suspected cases, and

individuals with prolonged close exposure to infected persons. Avoidance of rodents and rodent-contaminated environments in endemic regions remains the most important preventive strategy. Thus, effective containment depends largely on rapid identification, isolation, contact monitoring, and supportive medical care, including hemodynamic stabilization, respiratory support, and intensive care management in severe cases.


The current outbreak began aboard the Dutch expedition cruise vessel MV Hondius, which was traveling through Patagonia and Antarctic-associated routes after departing from South America. Passengers participated in excursions, including bird watching, in regions where Andes virus is known to exist naturally among wild rodents. Several travelers later developed fever and respiratory illness during the voyage. Initially, the illness was not recognized as hantavirus, and by the time laboratory testing confirmed Andes virus infection, some passengers had already returned to their home countries.

As of May 11, 2026, among the 147 passengers and crew members aboard the MV Hondius, a total of eight outbreak-associated cases have been reported, including six laboratory-confirmed infections with Andes hantavirus and two probable cases. Three deaths have occurred, including two laboratory-confirmed Andes virus fatalities and one probable death that remains under investigation.


At least thirty-four passengers had already traveled internationally before the outbreak was fully recognized, returning to countries including the United States, Canada, the United Kingdom, Switzerland, Australia, Singapore, and several European nations. Public health authorities subsequently initiated an extensive multinational contact-tracing operation. Although the international response has been coordinated and largely collegial, contact tracing has remained challenging and is still ongoing because several passengers disembarked earlier in the voyage and traveled through multiple countries, including exposure during commercial air travel and transit through international airports.

On May 10, the remaining 17 United States citizens aboard the MV Hondius, after surveillance and medical evaluation in Tenerife in the Canary Islands — which served as a medical evacuation and assessment zone — were transported to Omaha, Nebraska, for further observation and determination of additional public health measures.


Limited clinical and epidemiologic information is publicly available for only four confirmed cases, and several key aspects of the exposure history remain unresolved. Nevertheless, the available evidence suggests that Cases 1 (the presumed index patient) and 2 represented the earliest recognized infections and likely introduced the virus into the cruise-ship setting. It remains uncertain whether these individuals — as well as the other confirmed cases — acquired infection independently through environmental exposure during excursions in endemic regions of South America, or whether limited person-to-person transmission also occurred among individuals with prolonged close contact. Clarifying this distinction is epidemiologically important because it directly affects interpretation of the subsequent transmission dynamics observed aboard the vessel.


Investigators are examining cabin locations, travel activities, dining proximity, and viral genetic sequencing to better define how transmission occurred. It is also possible that the index patient functioned as a “super-spreader,” consistent with prior Andes virus outbreaks in South America in which transmission was amplified by a small number of highly infectious individuals during periods of close interpersonal contact. However, Current evidence suggests that secondary transmission aboard the vessel was limited or unlikely.


The outbreak has also drawn comparisons to a well-known Andes virus outbreak in Argentina described in the New England Journal of Medicine. That outbreak involved 34 confirmed cases and 11 deaths and provided the strongest evidence to date that Andes virus can occasionally spread between humans during prolonged close exposure in crowded indoor settings. However, important differences exist between that event and the current cruise-ship outbreak. The South American outbreak involved broader community exposure across multiple households, villages, and social gatherings, in a resource-limited setting, making containment far more difficult. In contrast, the approximately 147 travelers aboard the MV Hondius represent a relatively small and highly traceable group that was rapidly identified, monitored, isolated, and followed by international public health authorities. These factors make large secondary transmission chains far less likely and support current expert assessments that this outbreak does not pose a pandemic threat comparable to COVID-19.


Importantly, the Argentine Andes virus outbreak was ultimately brought under control within days after the implementation of classic public health measures, including case identification, isolation, contact tracing, and movement restrictions.


Another major question is whether the virus acquired genetic changes that enhanced its transmissibility. However, researchers studying viral genetic sequences from previous Andes virus outbreaks found little evidence that major viral mutations were necessary for human-to-human spread. Instead, environmental conditions, prolonged close contact, and crowded gatherings appear to have played a larger role in sustaining transmission during prior outbreaks. These findings suggest that transmission dynamics were more likely driven by patterns of human contact and exposure rather than by the emergence of a significantly altered viral genotype associated with enhanced transmissibility.


One more important question involves the possibility of rodent exposure aboard the vessel itself. Historically, ships have often been associated with rodents. However, the MV Hondius is a modern expedition vessel operating under strict sanitation and Antarctic biosecurity regulations. Investigators have not publicly identified evidence of rodent infestation aboard the ship, making widespread onboard environmental exposure less likely, although it has not been completely excluded.


Many exposed travelers remain asymptomatic, and no major secondary transmission chains have been identified. A French national is being monitored after possible exposure to Andes hantavirus during international air travel, a development drawing attention because Andes virus is the only hantavirus known to occasionally spread person-to-person. Importantly, the individual remains a contact case — not a confirmed infection — and tests to date have been negative. Public health agencies in multiple countries continue monitoring returning passengers and close contacts because the incubation period for Andes virus may extend for several weeks.


The most important message for the public is that Andes virus behaves very differently from highly contagious viruses such as measles or SARS-CoV-2. Current evidence suggests that Andes virus requires prolonged close exposure for transmission and does not spread efficiently through casual everyday contact. There is no evidence that airports, airplanes, schools, shopping centers, or ordinary public spaces are currently driving transmission.


At the same time, the outbreak serves as a reminder that infectious diseases remain deeply connected to globalization, environmental change, ecotourism, and international travel. Modern travel allows localized outbreaks to gain international attention within days, even when the actual risk to the broader public remains low.


The response to the outbreak also demonstrates how much global public health systems have evolved since the SARS and COVID-19 eras. International coordination, molecular diagnostics, surveillance systems, and rapid communication between countries were activated quickly once the diagnosis became clear.


The current situation does not justify panic or broad travel restrictions. However, it does reinforce the importance of continued surveillance, transparent scientific communication, international cooperation, and investment in global public health preparedness.


Here are five strong references that are readable, credible, and relevant:


A clear overview of hantavirus symptoms, transmission, prevention, and public health information for general readers.


The official World Health Organization outbreak summary and international risk assessment related to the MV Hondius outbreak.


A balanced, physician-reviewed article explaining the outbreak, transmission concerns, and why experts do not currently consider this a pandemic-level threat.


An important scientific paper documenting evidence for human-to-human transmission of Andes virus in Argentina.


5. Khan AS, Khabbaz RF, Armstrong LR, et al. Hantavirus Pulmonary Syndrome: The First 100 US Cases. Journal of Infectious Diseases. 1996;173(6):1297-1303. https://academic.oup.com/jid/article/173/6/1297/2190843


Author Bio



Majid Sadigh, MD, is the founding director of the Nuvance Health Global Health Academy. A physician-educator and humanitarian, he has devoted his career to advancing equitable global partnerships that train future leaders in medicine, education, and service.

 

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