Andes Hantavirus: Lessons from the 2018–2019 Argentina Outbreak and the 2026 MV Hondius Event

By Majid Sadigh, MD

Andes hantavirus (ANDV) is unique among hantaviruses because it is the only known species capable of sustained person-to-person transmission. Although such transmission remains uncommon, the virus poses a significant public health concern because of its high mortality rate, prolonged incubation period, and nonspecific early symptoms that can delay diagnosis.

The 2018–2019 outbreak in Argentina and the 2026 outbreak associated with the expedition vessel MV Hondius provide important comparative models for understanding the epidemiology, transmission dynamics, and global health implications of ANDV infection.

Available genomic analyses from both outbreaks demonstrated no major divergence from previously characterized Andes virus strains. Current evidence therefore does not suggest that the strain associated with the MV Hondius outbreak was inherently more transmissible or more virulent than earlier recognized strains.

Transmission is believed to occur primarily during the prodromal phase of illness, particularly within the first several days after symptom onset, when viral shedding may be greatest and infected individuals remain relatively mobile. Viral RNA has also been detected in blood shortly before symptom onset, although the epidemiologic significance of presymptomatic viremia remains uncertain.

Given these uncertainties, precautionary public health strategies remain appropriate. The European Centre for Disease Prevention and Control (ECDC)’s containment approach during the MV Hondius outbreak reflected a prudent risk-management strategy grounded in early isolation, intensive contact tracing, and international coordination.

The 2018–2019 Argentina Outbreak

The Argentina outbreak involved approximately 34 confirmed cases and 11 deaths, primarily in Patagonia. The outbreak is believed to have begun after an infected individual attended a large indoor birthday gathering in the town of Epuyén on November 3, 2018. The virus subsequently spread through close social and family interactions.

Transmission evolved through multiple sequential steps, beginning with rodent-to-human infection and progressing through secondary and tertiary person-to-person spread within interconnected rural communities. Several superspreading events were suspected, contributing to extensive transmission chains. One suspected superspreader was believed to have transmitted the virus to as many as nine individuals during a social gathering.

The outbreak occurred within an open geographic environment characterized by substantial movement between households and neighboring communities, complicating containment efforts. Prolonged close interpersonal contact during social events likely facilitated viral spread.

Despite these challenges, the outbreak was successfully controlled through rapid implementation of classic public health interventions, including case isolation, contact tracing, quarantine measures, and movement restrictions.

The 2026 MV Hondius Outbreak

In contrast, the MV Hondius outbreak appeared to represent a more geographically contained two-step epidemic: initial rodent-to-human acquisition in Argentina followed by person-to-person transmission aboard the vessel during prolonged close contact.

As of current reporting, the outbreak involved 9 confirmed cases, 2 probable cases, 1 inconclusive or under-investigation case, and 3 deaths among approximately 150 passengers and crew members. The presumed index patient was likely infected in Argentina before embarkation.

The cruise ship environment created conditions favorable for transmission because of prolonged interpersonal exposure, shared enclosed spaces, and repeated close interactions. Nevertheless, epidemiologic findings continued to support the conclusion that ANDV transmission requires sustained close contact rather than brief or casual exposure.

Unlike the outbreak in Argentina, no definitive superspreading event has yet been reported aboard the vessel.

The MV Hondius outbreak generated international concern because passengers and crew represented more than 20 nationalities. Following disembarkation in Saint Helena, exposed individuals traveled internationally through multiple transit hubs before returning to destinations across Europe, North America, Asia, and other regions.

These events highlighted how rapidly geographically localized outbreaks can become international public health concerns in an era of global mobility. At the same time, no evidence supported efficient airborne or casual-contact transmission, an observation critical for guiding proportionate public health responses and preventing unnecessary public alarm.

Public Health and Global Health Implications

Rapid international collaboration played a decisive role in limiting further spread during the MV Hondius outbreak. Coordinated contact tracing, transparent communication between nations, laboratory collaboration, and timely isolation measures significantly reduced the likelihood of sustained international transmission.

Together, these outbreaks reinforce several important epidemiologic principles. Andes virus is capable of person-to-person transmission under conditions of prolonged close exposure. Delayed recognition during the prodromal phase can facilitate transmission before diagnosis is established. Modern international travel can rapidly transform localized outbreaks into global public health concerns.

The MV Hondius event also serves as a reminder that infectious diseases no longer recognize geographic borders. In an interconnected world, the health of one population increasingly depends upon the vigilance, transparency, and cooperation of others.

Global health is therefore not only a scientific or political concept, but also an ethical recognition of our shared vulnerability and interdependence. Epidemics expose the fragility of human systems, yet they also demonstrate the strength that emerges through international collaboration. In an era defined by unprecedented mobility, global solidarity is no longer optional; it is essential for protecting public health and preserving our collective future.

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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.