Outbreak of Andes Virus Infection on Board MV Hondius, April – May 2026: Lessons for Biosafety Preparedness

Relevance. In April 2026, an outbreak of hantavirus infection caused by Andes virus (Orthohantavirus andesense) was reported on the expedition vessel MV Hondius, which had departed from the port of Ushuaia, Argentina, on 1 April 2026. Clinical symptoms in the first affected passenger appeared on 6 April, and the patient died on board the vessel on 11 April. In the following weeks, severe cases were identified among passengers and crew members after some individuals had disembarked and subsequently travelled through several countries. Aim. To assess the epidemiological and genomic characteristics of the outbreak and identify lessons for biosafety systems. Materials and Methods. We analyzed data from the epidemiological investigation provided by WHO and national health authorities. Genomic sequencing was performed using metagenomic approaches, SISPA, and hybridization enrichment. Phylogenetic analysis was conducted using the maximum likelihood method in IQ-TREE 3. Results and Discussion. Following outbreak investigation and diagnostic testing of patients in different countries, a total of 13 cases of infection were identified including 11 laboratory-confirmed cases, 2 probable cases, and 3 deaths. The epidemiological investigation suggests primary zoonotic infection of the index patient before boarding the vessel in an endemic area of southern Argentina, followed by limited person-to-person transmission on board. Genomic analysis demonstrated a high degree of identity among viral sequences obtained from affected individuals, which is consistent with a single introduction followed by subsequent human-to-human transmission. Conclusions. The hantavirus outbreak on board MV Hondius represents an important example of an epidemiologically significant event in which a zoonotic pathogen with limited capacity for person-to-person transmission occurred within a closed international community. This event highlights the importance of early clinical diagnosis, sanitary and quarantine measures for contact persons, and rapid international exchange of genomic data to ensure biosafety during epidemic events caused by emerging, rare, or genetically altered pathogens.

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