A Deadly Virus at Sea: The 2026 Hantavirus Outbreak on the M/V Hondius

In early May 2026, the world was warned of a group of severe cases of respiratory illness on a cruise ship on an ocean voyage to the South Atlantic Ocean, and the outbreak of infectious disease became the most widely monitored problem of the year, to date. It was the Andes virus — a rare and very dangerous type of hantavirus, and the ship at the heart of it — the Dutch-registered expedition cruise ship M/V Hondius.

Image from Wikipedia

On April 1, 2026, the Hondius had left Ushuaia, Argentina, with the 147 passengers and crew from 23 countries on the most daring of journeys: to Antarctica, South Georgia Island, Tristan da Cunha, Saint Helena, and Ascension Island. The first patients had illness onset between April 6 and April 28 with the following features: fever, gastrointestinal symptoms, and a rapid course of illness to pneumonia, acute respiratory distress syndrome, and shock. This was formally reported to the World Health Organization on 2nd May. On May 6, the WHO confirmed that the Andes virus is the culprit.

The European Centre for Disease Prevention and Control (ECDC) has confirmed 11 cases, with two more probable, and three deaths, as of 21 May 2026. There were no new cases or deaths in the preceding days to the update. The boat arrived in Rotterdam, the Netherlands, on May 18, and performed a thorough cleaning of the ship. May 10: CDC, in coordination with the state and federal partners, repatriated 18 American passengers who remained aboard the ship. As of May 18, no laboratory-confirmed cases of Andes virus associated with the outbreak have been detected in the United States, and the overall risk of the outbreak to the U.S. public remains very low, according to the CDC.

The Andes virus is particularly important from a public health perspective because it is the only known hantavirus that can spread between people. All other strains that have been discovered can only be spread to people by contact with infected rodents or droppings. However, human-to-human spread is uncommon and is likely to occur only with close contact over a prolonged period of time. However, the situation aboard a cruise ship was conducive to such contact. Diseases that can spread in close quarters on a cruise ship do not necessarily have the same mode of transmission in the community, said Dr. J. Lee Jenkins, deputy director of the Johns Hopkins Office of Critical Event Preparedness and Response, which is why public health officials aren’t treating it as a pandemic-level threat.

New World hantaviruses, such as Andes hantavirus, cause Hantavirus Pulmonary Syndrome, which has a severe clinical picture. Early signs and symptoms are similar to influenza (fever, muscle pains), and the illness can rapidly become life-threatening if it leads to respiratory failure. HPS due to hantaviruses in the United States (endemic) had a fatality rate of about 35% in the 864 cases reported in the last 30 years (1993–2022). With the speed at which the Hondius outbreak spread to the third death, it is no wonder that clinicians around the world were on high alert.

The incubation period of the Andes virus is also lengthy, so that passengers may have been disembarking while unwell but not showing symptoms. One passenger left the ship at Saint Helena on April 22 before the outbreak among the other passengers was officially announced, and then returned to Switzerland, where he ended up testing positive at the hospital in Zurich. Authorities are still tracking former passengers and contacts they have had in their travels by air around the world.

The current outbreak seems to be ‘contained’ for now. A reminder, however, of the power of remote travel, closed environments, and a pathogen that is potentially deadly and has even transmissible human-to-human properties.

Works Cited

“Andes Hantavirus Outbreak in Cruise Ship, May 2026.” European Centre for Disease Prevention and Control, 7 May 2026, www.ecdc.europa.eu/en/infectious-disease-topics/hantavirus-infection/surveillance-and-updates/andes-hantavirus-outbreak. Accessed 23 May 2026.

“Hantavirus Cluster Linked to Cruise Ship Travel, Multi-Country.” Disease Outbreak News, World Health Organization, 4 May 2026, www.who.int/emergencies/disease-outbreak-news/item/2026-DON599. Accessed 23 May 2026.

“Hantavirus: Current Situation.” Hantavirus, Centers for Disease Control and Prevention, 8 May 2026, www.cdc.gov/hantavirus/situation-summary/index.html. Accessed 23 May 2026.

Jenkins, J. Lee. “Hantavirus Outbreak 2026.” Hopkins Medicine, Johns Hopkins Medicine, 2026, www.hopkinsmedicine.org/health/expert-qa/hantavirus. Accessed 23 May 2026.

Ismail, Nazir Ahmed, et al. “Andes Hantavirus Outbreak on a Cruise Ship, 2026.” New England Journal of Medicine, 21 May 2026, www.nejm.org/doi/full/10.1056/NEJMc2606496. Accessed 23 May 2026.