On 1 April 2026, the MV Hondius — a Dutch-flagged expedition cruise ship operated by Oceanwide Expeditions — departed the Argentine port city of Ushuaia for a 33-day voyage north through the Atlantic. Among its 86 passengers, boarded from 23 countries, was a Dutch man in his 70s who had spent several months traveling through Argentina and Chile before joining the voyage. He was, at the time, feeling well. He would be dead within 11 days of departure.
The sequence of events that followed — spanning four deaths, eight countries of hospitalization, and a 22-nation repatriation effort — constitutes the most internationally complex hantavirus outbreak ever recorded.
The index case — the first person infected, from whom the outbreak originated — is a Dutch male passenger, 70 years old, who had been on an extended road trip through Argentina and Chile for several months before boarding the MV Hondius. According to WHO Director-General Dr. Tedros Adhanom Ghebreyesus at a press briefing on 7 May 2026, the most likely source of exposure was a birdwatching excursion near a landfill on the outskirts of Ushuaia.
Landfill environments in Patagonia are known habitats for the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), the primary rodent reservoir for Andes virus. Argentine authorities subsequently began rodent trapping along the route to confirm the presence of infected animals. At the time of writing, no confirmed rodent source has been publicly identified, but the epidemiological circumstances — an individual with prolonged exposure to rural Patagonian environments, in a region where Andes virus is endemic — are consistent with this transmission route.
Hantavirus has an incubation period of one to eight weeks, meaning the index case was almost certainly already infected when he boarded on 1 April 2026, and was still asymptomatic. He developed symptoms around 6 April. By 11 April, he had died aboard the vessel — with hantavirus not yet suspected. His cause of death was initially recorded as respiratory illness.
The confined environment of the cruise ship — shared dining rooms, lounges, and cabin corridors — created conditions that facilitated Andes virus's rare person-to-person transmission mode. His wife, a Dutch woman of 69, developed symptoms and was evacuated to a hospital in Johannesburg when the ship stopped at Saint Helena on 24 April. She died on 26 April, becoming the second fatality and the first case confirmed by PCR as Andes virus. A third passenger — a German woman — died aboard the vessel on 2 May.
The Netherlands formally notified WHO on 2 May 2026 via the International Health Regulations (IHR) mechanism. WHO published its first Disease Outbreak News report (DON599) on 4 May. The international response that followed was remarkable in its scale and coordination:
The publication of the full Andes virus genome from the MV Hondius outbreak on virological.org by Swiss researchers — designated ANDV/Switzerland/Hu-3337/2026 — allowed virologists to compare the shipboard strain with previously sequenced Andes virus isolates from South America. The Pathoplexus team subsequently analyzed sequences from five patients (two from Johannesburg, two from the Netherlands, one Swiss) and confirmed they represent a single introduction event — all passengers were infected from the same source, consistent with a single index case.
As of the time of writing, several significant questions about the MV Hondius outbreak remain under investigation:
The MV Hondius event is a case study in how a localized zoonotic exposure in a remote part of the world can rapidly become a multinational public health emergency. A single person, infected during an outdoor activity in Argentine Patagonia, carried a dangerous pathogen onto an international vessel and — through a combination of the ship's enclosed environment and Andes virus's unusual person-to-person transmission capability — seeded cases across Europe and beyond.
For most people in the world, the risk from this outbreak is negligible. WHO's global risk assessment of LOW reflects the scientific consensus that Andes virus does not spread casually. But the outbreak has exposed gaps in international surveillance for travel-associated zoonotic diseases, and it has demonstrated the critical importance of rapid IHR notification and international coordination when a novel cluster is identified at sea.
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